WO2021261412A1

WO2021261412A1 - Method for producing polyester film, polyester film, laminated film

Info

Publication number: WO2021261412A1
Application number: PCT/JP2021/023294
Authority: WO
Inventors: 佑記福岡; 享春永尾
Original assignee: 富士フイルム株式会社
Priority date: 2020-06-24
Filing date: 2021-06-21
Publication date: 2021-12-30
Also published as: TW202216863A; KR20230011388A; JPWO2021261412A1; CN115943032A; JP7428798B2

Abstract

The present invention addresses the problem of providing: a method for producing a polyester film capable of further suppressing uneven thickness of a functional layer provided on the surface of a polyester film; and a polyester film and a laminated film capable of further suppressing uneven thickness of a functional layer provided on the surface.　The method for producing a polyester film of the present invention has an extrusion molding step for extruding a molten resin containing a polyester into a film to form an unoriented polyester film; a longitudinal orientation step for orienting the unoriented polyester film in the transport direction; a widthwise orientation step for orienting the uniaxially oriented polyester film in the width direction; a heat fixation step for heating to heat fix the biaxially oriented polyester film; a heat relaxation step for heating at a lower temperature than the heat fixation step to heat relax the heat-fixed polyester film; a cooling step for cooling the heat-relaxed polyester film; an expansion step for expanding the heat-relaxed polyester film in the width direction in the cooling step; and a particle-containing layer formation step for providing a particle-containing layer that contains particles on at least one surface of the polyester base material, the cooling velocity of the polyester film in the cooling step being 2200-3500°C/min and satisfying the following specific condition 1.

Description

Manufacturing method of polyester film, polyester film, laminated film

The present invention relates to a method for manufacturing a polyester film, a polyester film, and a laminated film.

Biaxially oriented polyester films are used in a wide range of applications from the viewpoints of processability, mechanical properties, electrical properties, dimensional stability, transparency, chemical resistance, etc., for example, decorative films and dry films. It is used in various applications such as a support for a photoresist, a protective film, a magnetic tape, and a release film used for producing a ceramic green sheet for manufacturing a laminated ceramic capacitor.

On the other hand, in the manufacturing process of the biaxially oriented polyester film, a technique of providing a particle-containing layer on the surface is known as a technique of suppressing the generation of wrinkles (conveyed wrinkles) that occur during the transfer of the polyester film.
For example, Patent Document 1 describes a biaxially oriented polyester film in which a slippery resin layer having an average thickness of 3 to 80 nm is laminated on the opposite side of a resist-coated surface, which does not contain particles having an average particle size of more than 40 nm. Disclosed is a polyester film for a photoresist in which a 10-point average roughness (SRz), haze, static friction coefficient (μs), and heat shrinkage stress at 150 ° C. on the slippery resin layer side of the polyester film are specified.

Japanese Unexamined Patent Publication No. 2004-361446

The present inventors further investigated a method for producing a polyester film having a particle-containing layer with reference to the technique described in Patent Document 1, and found that a functional layer was formed on a biaxially oriented polyester film to form a laminated film. During production, a liquid composition (for example, a coating liquid) is applied to the surface of the biaxially oriented polyester film and heat-treated, even though unevenness or wrinkles are not visible before the functional layer is formed. It was found that uneven thickness of the functional layer may occur in the laminated film after the functional layer is formed.
Such uneven thickness of the functional layer is, for example, in a decorative film having a decorative layer as the functional layer, the uneven thickness of the decorative layer is expressed as color unevenness, which may reduce the visibility of the decorative film. .. Further, if the thickness unevenness occurs in other functional layers, it may affect the characteristics or appearance of the laminated film having functionality.

In view of the above circumstances, it is an object of the present invention to provide a method for producing a polyester film capable of further suppressing the thickness unevenness of the functional layer provided on the surface of the polyester film.
Another object of the present invention is to provide a polyester film and a laminated film capable of further suppressing the thickness unevenness of the functional layer provided on the surface.

As a result of diligent studies on the above problems, the present inventors have found that the above problems can be solved by the following configuration.

[1]
An extrusion molding step of extruding a molten resin containing polyester into a film to form an unstretched polyester film containing at least a polyester base material, and stretching the unstretched polyester film in a transport direction to form a uniaxially oriented polyester film. A longitudinal stretching step, a transverse stretching step of stretching the uniaxially oriented polyester film in the width direction to form a biaxially oriented polyester film, and a heat fixing step of heating and heat-fixing the biaxially oriented polyester film. A heat relaxation step of heating the polyester film heat-fixed by the heat-fixing step at a temperature lower than that of the heat-fixing step to relax the heat, and a cooling step of cooling the heat-relaxed polyester film by the heat-relaxing step. In the cooling step, a polyester base material having an expansion step of expanding the heat-relaxed polyester film in the width direction, and a particle-containing layer containing particles on at least one surface of the polyester base material. Is a method for producing a polyester film having,
A method for producing a polyester film, wherein the cooling rate V of the polyester film in the cooling step is 2200 to 3500 ° C./min, and the condition 1 described later is satisfied.
[2]
The manufacturing method according to [1], wherein the value D calculated from the above-mentioned A, the above-mentioned B, and the above-mentioned cooling rate V by the formula (3) described later is 1 to 10000.
[3]
The production method according to [1] or [2], wherein the thickness of the polyester film is less than 50 μm.
[4]
Between the longitudinal stretching step and the transverse stretching step, there is a further step of forming the particle-containing layer using the coating liquid containing the particles, or in the extrusion molding step, the particles and the binder are used. The production method according to any one of [1] to [3], further comprising a step of forming the particle-containing layer by extruding the contained second melt at the same time as the molten resin.
[5]
The production method according to any one of [1] to [4], wherein the surface temperature T2 of the polyester film in the heat relaxation step is 210 ° C. or lower.
[6]
The production method according to any one of [1] to [5], wherein the cooling rate V of the polyester film by the cooling step is 2200 to 3000 ° C./min.
[7]
The production method according to any one of [1] to [6], wherein b is more than 0% and 1.2% or less.
[8]
A polyester film having a polyester base material and a particle-containing layer containing particles on the surface of at least one of the polyester base materials, wherein the thickness of the polyester film is less than 50 μm, and the polyester film has a thickness of less than 50 μm. On the other hand, the polyester film was heat-treated for 20 seconds under the condition that the temperature of the film surface was 90 ° C. while transporting under the conditions of a transport speed of 30 m / min and a tension of 100 N / m in the transport direction. A polyester film in which the total area of streaky defect regions observed in is 40% or less of the total area of the observed region.
[9]
The polyester film according to [8], wherein the expansion rate in the width direction of the polyester film at 90 ° C. is −0.15 to 0.15% with respect to the dimension in the width direction of the polyester film at 30 ° C.
[10]
The polyester film according to [8] or [9], wherein the polyester film has a density of 1.39 to 1.41 g / cm ^3.
[11]
The polyester film according to any one of [8] to [10], wherein the polyester base material has a thickness of 3 to 40 μm and the particle-containing layer has a thickness of 0.001 to 2.5 μm.
[12]
The polyester film according to any one of [8] to [11], wherein the particle-containing layer contains particles P having an average particle diameter of 10 nm or more and less than 1 μm.
[13]
The polyester film according to [12], wherein the average particle diameter of the particles P is larger than the thickness of the particle-containing layer.
[14]
The polyester film according to any one of [8] to [13], wherein the particle-containing layer contains particles P1 having an average particle diameter of 10 to 100 nm.
[15]
The polyester film according to any one of [8] to [14], wherein the particle-containing layer contains particles P2 having an average particle diameter of more than 100 nm and 400 nm or less.
[16]
The particles contained in the particle-containing layer are resin particles, or the particles contained in the particle-containing layer are inorganic particles, and the maximum mountain height Rp of at least one surface of the polyester film is 5 to 200 nm. , [8] to [15].
[17]
The polyester film according to any one of [8] to [16], wherein the polyester substrate does not substantially contain particles.
[18]
The polyester film produced by the production method according to any one of [1] to [7], or the polyester film according to any one of [8] to [17], which is one surface of a polyester base material. It is on the surface opposite to the particle-containing layer of the polyester base material and the polyester film having the particle-containing layer only on the top, and is selected from the group consisting of a decorative layer, a photosensitive resin layer, and a peeling layer. A laminated film having a functional layer and.
[19]
The laminated film according to [18], wherein the functional layer is a decorative layer and the laminated film is a decorative film.
[20]
The laminated film according to [18], wherein the functional layer is a photosensitive resin layer and the laminated film is a photosensitive transfer film.
[21]
The laminated film according to [18], wherein the functional layer is a release layer and the laminated film is a release film for manufacturing a ceramic green sheet.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for producing a polyester film capable of further suppressing the thickness unevenness of the functional layer provided on the surface of the polyester film.
Further, according to the present invention, it is possible to provide a polyester film and a laminated film capable of further suppressing the thickness unevenness of the functional layer provided on the surface.

It is an observation image of a polyester film in which a streak defect region was generated. It is a top view which shows an example of the stretching machine used for manufacturing a polyester film.

Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be carried out with appropriate modifications within the scope of the object of the present invention.

In the present disclosure, the numerical range represented by using "-" means a range including the numerical values before and after "-" as the lower limit value and the upper limit value. In the numerical range described stepwise in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in another stepwise description. Further, in the numerical range described in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples.
In the present disclosure, the amount of each component in the composition means the total amount of the plurality of substances present in the composition when a plurality of substances corresponding to each component are present in the composition, unless otherwise specified. ..
In the present disclosure, the term "process" is included in this term not only as an independent process but also as long as the intended purpose of the process is achieved even if it cannot be clearly distinguished from other processes. ..
In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

In the present disclosure, the description of a mere "polyester film" includes both a polyester base material alone and a laminate of a polyester base material and a particle-containing layer.
In the present disclosure, the "longitudinal direction" means the elongated direction of the polyester film at the time of manufacturing the polyester film, and is synonymous with the "transport direction" and the "mechanical direction".
In the present disclosure, the "width direction" means a direction orthogonal to the longitudinal direction. In the present disclosure, "orthogonal" is not limited to strict orthogonality, but includes substantially orthogonality. “Approximately orthogonal” means intersecting at 90 ° ± 5 °, preferably 90 ° ± 3 °, and more preferably 90 ° ± 1 °.
Further, in the present disclosure, the "film width" means the distance between both ends of the polyester film in the width direction.

[Polyester film]
The polyester film according to the present disclosure (hereinafter, also referred to as "the present film") has at least a polyester base material and a particle-containing layer on the surface of at least one of the polyester base materials and containing particles.
In an example of the embodiment of this film, the thickness of the polyester film is less than 50 μm, and the area of the streak defect region observed in the heat-treated polyester film described later is 40 with respect to the total area of the observation region. % Or less.

〔structure〕
As described above, the film has a polyester substrate and a particle-containing layer on at least one surface of the substrate. The particle-containing layer may be formed on only one surface of the polyester base material, or may be formed on both sides of the polyester base material.
Hereinafter, each of the polyester base material and the particle-containing layer will be described in more detail.

<Polyester base material>
The polyester base material is a film-like object containing polyester as a main polymer component. Here, the "main polymer component" means the polymer having the highest content (mass) among all the polymers contained in the film.
The polyester base material may contain one kind of polyester alone or may contain two or more kinds of polyesters.

(polyester)
Polyester is a polymer having an ester bond in the main chain. Polyester is usually formed by polycondensing a dicarboxylic acid compound and a diol compound, which will be described later.
The polyester is not particularly limited, and known polyesters can be used. Examples of the polyester include polyethylene terephthalate (PET), polyethylene-2,6-naphthalate (PEN), polypropylene terephthalate (PPT), polybutylene terephthalate (PBT) and copolymers thereof, and among them, polyethylene. At least one selected from the group consisting of terephthalate (PET), polyethylene-2,6-naphthalate (PEN), and polymers thereof is preferable, and PET is more preferable.

The intrinsic viscosity of the polyester is preferably 0.50 dl / g or more and less than 0.80 dl / g, and more preferably 0.55 dl / g or more and less than 0.70 dl / g.
The melting point (Tm) of the polyester is preferably 220 to 270 ° C, more preferably 245 to 265 ° C.
The glass transition temperature (Tg) of polyester is preferably 65 to 90 ° C, more preferably 70 to 85 ° C.

The method for producing polyester is not particularly limited, and a known method can be used. For example, polyester can be produced by polycondensing at least one dicarboxylic acid compound and at least one diol compound in the presence of a catalyst.

-catalyst-
The catalyst used for producing the polyester is not particularly limited, and a known catalyst that can be used for synthesizing the polyester can be used.
Examples of the catalyst include alkali metal compounds (for example, potassium compounds and sodium compounds), alkaline earth metal compounds (for example, calcium compounds and magnesium compounds), zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, and antimony compounds. Examples thereof include compounds, titanium compounds, germanium compounds and phosphorus compounds. Of these, titanium compounds are preferable from the viewpoint of catalytic activity and cost.
Only one type of catalyst may be used, or two or more types may be used in combination. At least one metal catalyst selected from potassium compound, sodium compound, calcium compound, magnesium compound, zinc compound, lead compound, manganese compound, cobalt compound, aluminum compound, antimony compound, titanium compound, germanium compound, and phosphorus compound. It is preferable to use in combination, and it is more preferable to use a titanium compound and a phosphorus compound in combination.

As the titanium compound, an organic chelated titanium complex is preferable. The organic chelated titanium complex is a titanium compound having an organic acid as a ligand.
Examples of the organic acid include citric acid, lactic acid, trimellitic acid, and malic acid.
As the titanium compound, the titanium compounds described in paragraphs 0049 to 0053 of Japanese Patent No. 5575671 can also be used, and the contents of the above publication are incorporated in the present specification.

-Dicarboxylic acid compound-
The dicarboxylic acid compound is preferably a dicarboxylic acid or a dicarboxylic acid ester, and examples thereof include an aliphatic dicarboxylic acid compound, an alicyclic dicarboxylic acid compound, an aromatic dicarboxylic acid compound, and a methyl ester compound or an ethyl ester compound thereof. .. Of these, aromatic dicarboxylic acid or methyl aromatic dicarboxylic acid is more preferable.

Examples of the aliphatic dicarboxylic acid compound include malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecandionic acid, dimer acid, eicosandionic acid, pimelic acid, azelaic acid, and methylmalonic acid. And ethylmalonic acid.
Examples of the alicyclic dicarboxylic acid compound include adamantandicarboxylic acid, norbornenedicarboxylic acid, cyclohexanedicarboxylic acid, and decalindicarboxylic acid.

Examples of the aromatic dicarboxylic acid compound include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 1,8-naphthalenedicarboxylic acid. , 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 5-sodium sulfoisophthalic acid, phenylindandandicarboxylic acid, anthracendicarboxylic acid, phenanthrangecarboxylic acid, 9,9'-bis (4-carboxyphenyl) ) Dicarboxylic acids and their methyl ester forms are mentioned.
Of these, terephthalic acid or 2,6-naphthalenedicarboxylic acid is preferable, and terephthalic acid is more preferable.

Only one type of dicarboxylic acid compound may be used, or two or more types may be used in combination. When terephthalic acid is used as the dicarboxylic acid compound, terephthalic acid may be used alone, or it may be copolymerized with another aromatic dicarboxylic acid such as isophthalic acid or an aliphatic dicarboxylic acid.

-Diol compound-
Examples of the diol compound include an aliphatic diol compound, an alicyclic diol compound, and an aromatic diol compound, and an aliphatic diol compound is preferable.

Examples of the aliphatic diol compound include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, 1,3-butanediol, and neo. Examples thereof include pentyl glycol, and ethylene glycol is preferable.
Examples of the alicyclic diol compound include cyclohexanedimethanol, spiroglycol, and isosorbide.
Examples of the aromatic diol compound include bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, and 9,9'-bis (4-hydroxyphenyl) fluorene.
Only one kind of diol compound may be used, or two or more kinds may be used in combination.

-End sealant-
In the production of polyester, an end-capping agent may be used if necessary. By using the end sealant, a structure derived from the end sealant is introduced into the end of the polyester.
As the terminal encapsulant, a known end encapsulant can be used without limitation. Examples of the terminal encapsulant include oxazoline compounds, carbodiimide compounds, and epoxy compounds.
As the terminal encapsulant, the contents described in paragraphs 0055 to 0064 of JP-A-2014-189002 can also be referred to, and the contents of the above-mentioned publication are incorporated in the present specification.

-Manufacturing conditions-
The reaction temperature is not limited and may be appropriately set according to the raw material. The reaction temperature is preferably 260 to 300 ° C, more preferably 275 to 285 ° C.
The pressure is not limited and may be set appropriately according to the raw material. The pressure is ^{preferably 1.33 × 10 -3} to 1.33 × 10 ^-5 MPa, more preferably 6.67 × 10 ^-4 to 6.67 × 10 ^-5 MPa.

As a method for synthesizing polyester, the methods described in paragraphs 0033 to 0070 of Japanese Patent No. 5575671 can also be used, and the contents of the above publication are incorporated in the present specification.

The polyester content in the polyester base material is preferably 85% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, still more preferably 98% by mass, based on the total mass of the polymer in the polyester base material. The above is particularly preferable.
The upper limit of the polyester content is not limited and can be appropriately set within a range of 100% by mass or less with respect to the total mass of the polymer in the polyester substrate.

When the polyester base material contains polyethylene terephthalate, the content of polyethylene terephthalate is preferably 90 to 100% by mass, more preferably 95 to 100% by mass, and 98 to 90 to the total mass of the polyester in the polyester base material. 100% by mass is more preferable, and 100% by mass is particularly preferable.

The polyester base material may contain components other than polyester (for example, catalyst, unreacted raw material component, water, etc.).
The polyester substrate preferably contains substantially no particles. Here, "substantially free of particles" means that the content of particles is a polyester group when the elements derived from the particles are quantitatively analyzed by fluorescent X-ray analysis for both the polyester base material and the particle-containing layer. It is defined as 50 mass ppm or less with respect to the total mass of the material, preferably 10 mass ppm or less, and more preferably the detection limit or less. This means that even if particles are not actively added to the base film, contamination components derived from foreign substances or stains adhering to the raw material resin or the line or device in the manufacturing process of the film are peeled off and into the film. This is because it may be mixed.

The thickness of the polyester base material is preferably 100 μm or less, more preferably 50 μm or less, still more preferably 40 μm or less, in that an increase in haze value can be suppressed. The lower limit of the thickness is not particularly limited, but 3 μm or more is preferable, 4 μm or more is more preferable, and 10 μm or more is further preferable, in terms of improving the strength and the workability.
The thickness of the polyester base material is measured according to the method for measuring the thickness of the polyester film described later.

<Particle-containing layer>
The particle-containing layer is a layer containing particles and is formed on at least one surface of a polyester substrate. The present film can improve the transportability by having a particle-containing layer. More specifically, it is possible to improve the winding quality (suppress blocking), suppress the occurrence of scratches and defects during transport, and reduce transport wrinkles.
The particle-containing layer may be provided directly on the surface of the polyester base material or may be provided on the surface of the polyester base material via another layer, but the particle-containing layer may be provided directly on the surface of the polyester base material in terms of better adhesion. It is preferable to provide it.

Examples of the particles contained in the particle-containing layer include organic particles and inorganic particles. Among them, inorganic particles are preferable from the viewpoint of further improving film winding quality, haze, and durability (for example, thermal stability).
As the organic particles, resin particles are preferable. Examples of the resin constituting the resin particles include acrylic resins such as polymethyl methacrylate resin (PMMA), polyester resins, silicone resins, and styrene-acrylic resins. The resin particles preferably have a crosslinked structure. Examples of the resin particles having a crosslinked structure include divinylbenzene crosslinked particles having a crosslinked structure derived from divinylbenzene (for example, divinylbenzene / styrene copolymer crosslinked particles). Resin particles are preferable from the viewpoint of suppressing transfer marks.
Examples of the inorganic particles include silica particles (silicon dioxide particles), titania particles (titanium oxide particles), calcium carbonate, barium sulfate, and alumina particles (aluminum oxide particles). Among the above, the inorganic particles are preferably silica particles from the viewpoint of further improving haze and durability.

The shape of the particles is not particularly limited, and examples thereof include rice granules, spheres, cubes, spindles, scales, agglutinates, and indefinite shapes. The aggregated state means a state in which the primary particles are aggregated. The shape of the aggregated particles is not limited, but a spherical or irregular shape is preferable.

For the particle-containing layer, it is preferable to form a coating liquid having at least one of aggregated particles and non-aggregated particles by in-line coating. Here, the agglomerated particles mean particles that are in the agglomerated state in the coating liquid, and the non-aggregating particles mean particles that are not in the agglomerated state in the coating liquid.

As the agglomerated particles, fumed silica particles are preferably mentioned. Examples of commercially available products include Aerosil series manufactured by Nippon Aerosil Co., Ltd.
Preferred examples of the non-aggregated particles include colloidal silica particles. Examples of commercially available products include the Snowtex series manufactured by Nissan Chemical Industries, Ltd.

The particle-containing layer may contain one type of particles alone or may contain two or more types of particles.
The particle content is preferably 0.01 to 20% by mass, preferably 0.5 to 15% by mass, based on the total mass of the particle-containing layer from the viewpoint of improving the winding quality of the film and suppressing transfer defects. Is more preferable, and 1 to 10% by mass is further preferable.
The content of the particles is preferably 0.0001 to 0.01% by mass, more preferably 0.0005 to 0.005% by mass, based on the total mass of the polyester film.

(Particle P)
The particle-containing layer preferably contains particles P having an average particle diameter of 10 nm or more and less than 1 μm in terms of improving winding quality and suppressing transfer failure.
The average particle size of the particles P is preferably 0.03 μm or more in that the winding quality can be further improved. The average particle size of the particles P is preferably 0.4 μm or less, more preferably 0.25 μm or less, in that transfer failure can be further suppressed.
Further, in one embodiment, it is preferable that the average particle size of the particles P is larger than the thickness of the particle-containing layer in terms of improving the transportability and the winding quality. In other words, the particle-containing layer preferably contains particles P having an average particle size of 10 nm or more and less than 1 μm and an average particle size larger than the thickness of the particle-containing layer.

When the particle-containing layer contains two or more kinds of particles having different particle sizes, it is preferable that at least one kind of two or more kinds of particles having different particle sizes is particles P, and transfer failure and winding quality are further improved. From this viewpoint, it is more preferable that the particle-containing layer contains two or more kinds of particles P having different particle diameters.

The average particle size of the particles contained in the particle-containing layer can be determined by the following method using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). That is, the cross section of the particle-containing layer is observed by SEM or TEM, and the area of each particle is measured using image software for all the particles existing in the field of view of 3 μm × 4 μm, and the diameter of the circle having the same area. (Area circle equivalent diameter) is calculated, and the calculated average value of the obtained area circle equivalent diameter is used as the average particle diameter of the particles.
In the measurement of the average particle size, for the agglomerated particles, the particle size (secondary particle size) of the secondary particles in the agglomerated state shall be measured.
Further, when the particle-containing layer contains two or more kinds of particles having different particle diameters, two or more peaks having different particle diameters can be seen in the distribution of the area equivalent circle diameter measured by the above measuring method. In this way, when the distribution of the area circle equivalent diameter measured by the above measurement method has two or more peaks with different particle diameters, the average value of the area circle equivalent diameter is calculated for each peak. Therefore, the average particle size shall be calculated for each particle with a different particle size.

The particle-containing layer may contain one type of single particle P, or may contain two or more types of particle P.
The content of the particles P may be the same as the content of the above-mentioned particles, including the preferred embodiment thereof.

In certain embodiments, the particle-containing layer preferably contains particles having a small average particle diameter (hereinafter, also referred to as “particle P1”) from the viewpoint of transparency and transfer failure. Specifically, the particle-containing layer preferably contains particles having an average particle diameter of 100 nm or less, and more preferably particles having an average particle diameter of 70 nm or less, as the particles P1. The lower limit of the particles P1 is not particularly limited, but 10 nm or more is preferable from the viewpoint of further improving the winding quality.

The particle P1 may be used alone or in combination of two or more.
The content of the particles P1 varies depending on the purpose and / or use of the polyester film, but is preferably 0.01 to 20% by mass, more preferably 0.5 to 15% by mass, based on the total mass of the particle-containing layer. 1 to 10% by mass is more preferable.

In a certain embodiment, the particle-containing layer preferably contains particles having a large average particle diameter (hereinafter, also referred to as “particle P2”) from the viewpoint of improving the winding quality. Specifically, the particle-containing layer preferably contains particles having an average particle diameter of more than 100 nm as the particles P2. The upper limit of the particles P2 is not particularly limited, but is preferably less than 1 μm, more preferably 400 nm or less, still more preferably 250 nm or less, from the viewpoint of further improving transfer failure and winding quality.

The particles P2 may be aggregated particles or non-aggregated particles, but are preferably aggregated particles from the viewpoint of transfer failure.
The aggregated particles as the particles P2 preferably have an average secondary particle diameter of more than 100 nm. Further, as the agglomerated particles, it is preferable that particles having an average primary particle diameter of 100 nm or less are agglomerated. When aggregated particles having an average primary particle diameter of 100 nm or less and having an average secondary particle diameter of more than 100 nm are used, the desired Rp is obtained especially when a particle-containing layer is formed by in-line coating. It is possible to improve transfer failure and winding quality.

The particles P2 may be used alone or in combination of two or more.
The content of the particles P2 varies depending on the purpose and / or use of the polyester film, but is preferably 0.01 to 15% by mass, more preferably 0.05 to 10% by mass, based on the total mass of the particle-containing layer. It is more preferably 0.1 to 5% by mass.

The particle-containing layer preferably contains at least one kind of particle P1 and at least one kind of particle P2 from the viewpoint of further improving transfer failure and winding quality.

The particles contained in the particle-containing layer can be appropriately selected depending on the purpose and / or use.
When used as a support for a dry film resist for forming a fine pattern, the support may have pattern defects if particles are scattered when exposed through the support. High transparency is required. From the viewpoint of further improving the transparency, the content of the particles P1 is preferably 50 to 100% by mass, preferably 70 to 100% by mass, based on the total content of all the particles contained in the particle-containing layer. Is more preferable.
In this case, the balance is preferably particles P2.

On the other hand, when it is necessary to transport at a higher speed for the purpose of improving productivity, high transportability is required. From the viewpoint of further improving the transportability, the content of the particles P2 is preferably 10 to 100% by mass, preferably 10 to 50% by mass, based on the total content of all the particles contained in the particle-containing layer. Is more preferable, and 10 to 30% by mass is further preferable.
In this case, the balance is preferably particles P1.

(binder)
The particle-containing layer preferably contains a binder. As the binder, a resin binder is preferable. Examples of the resin binder include polyacrylic acid, polyurethane, polyester and polyolefin.

The polyacrylic acid is not limited as long as it is a polymer having a structural unit derived from at least one compound selected from the group consisting of an acrylic acid ester and a methacrylic acid ester, and known polyacrylic acid can be used. Polyacrylic acid may have a structural unit derived from a compound other than the acrylic acid ester and the methacrylic acid ester (for example, an olefin compound and a styrene compound).
The polyurethane is not limited as long as it is a polymer having a urethane bond, and known polyurethane can be used. Polyurethane is usually produced by reacting an isocyanate compound with a polyol compound.
As the polyester, the polyester described in the above item "Polyester" can be applied, and the preferred type is also the same.
The polyolefin is not limited, and known polyolefins can be used. Examples of the polyolefin include polyethylene and polypropylene.

The particle-containing layer may contain one kind of binder alone or may contain two or more kinds of binders.
The content of the binder is preferably 30 to 99.8% by mass, preferably 50 to 99.5% by mass, based on the total mass of the particle-containing layer, from the viewpoint of the durability of the particle-containing layer and / or the dispersibility of the particles. Is more preferable.

(Additive)
The particle-containing layer may contain additives other than the above particles and binder.
Additives contained in the particle-containing layer include, for example, surfactants, waxes, cross-linking agents, antioxidants, UV absorbers, colorants, strengthening agents, plasticizers, antistatic agents, flame retardants, and rust preventives. , And antistatic agents.

The surfactant is not particularly limited, and examples thereof include an anionic surfactant, a nonionic surfactant, a cationic surfactant, and an amphoteric surfactant.
One type of surfactant may be used, or two or more types may be used in combination.
The content of the surfactant is preferably 0.1 to 10% by mass with respect to the total mass of the particle-containing layer.

The wax is not particularly limited, and may be a natural wax or a synthetic wax. Examples of the natural wax include carnauba wax, candelilla wax, beeswax, montan wax, paraffin wax, and petroleum wax. In addition, the slip agent described in [0087] of International Publication No. 2017/169844 can also be used.
The wax content is preferably 0 to 10% by mass with respect to the total mass of the particle-containing layer.

The cross-linking agent is not particularly limited, and known ones can be used.
Examples of the cross-linking agent include melamine compounds, oxazoline compounds, epoxy compounds, isocyanate compounds, and carbodiimide-based compounds, and oxazoline-based compounds and carbodiimide-based compounds are preferable. Examples of commercially available products include Carbodilite V-02-L2 (manufactured by Nisshinbo Co., Ltd.) and Epocross K-2020E (manufactured by Nippon Shokubai Co., Ltd.). For details of the epoxy-based compound, the isocyanate-based compound, and the melamine-based compound, the description of [0081] to [0083] of JP2015-163457 can be referred to. The cross-linking agent described in [2002] to [0084] of International Publication No. 2017/169844 can also be preferably used. As the carbodiimide compound, the description of [0038] to [0040] of JP-A-2017-087421 can be referred to.
For the oxazoline compound, the carbodiimide compound, and the isocyanate compound, the cross-linking agent described in [0074] to [0075] of International Publication No. 2018/034294 can also be preferably used.
The content of the cross-linking agent can be appropriately changed depending on the intended use, and is preferably 0 to 50% by mass with respect to the total mass of the particle-containing layer. From the viewpoint of being suitable as a support for a dry film, the content of the cross-linking agent is preferably 0.1 to 10% by mass with respect to the total mass of the particle-containing layer.

The thickness of the particle-containing layer may be 0.001 to 5 μm, but from the viewpoint of manufacturing suitability of the particle-containing layer and reduction of haze, 0.001 to 2.5 μm is preferable, and 0.005 to 2 9.0 μm is more preferable, 0.01 to 0.18 μm is further preferable, and 0.01 to 0.1 μm is particularly preferable.
The thickness of the particle-containing layer is an arithmetic average value of five thicknesses measured using a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

The method for forming the particle-containing layer will be described in detail in the "particle-containing layer forming step" described later.

This film may have a layer other than the polyester base material and the particle-containing layer, but is preferably composed of the polyester base material and the particle-containing layer. Further, it is preferable that the present film has only one particle-containing layer formed on one surface of the polyester base material.

[Physical characteristics, etc.]
Next, the physical characteristics of this film will be described.

(Orientation)
This film is a biaxially oriented polyester film. In the present disclosure, "biaxial orientation" means a property having molecular orientation in the biaxial direction.
The molecular orientation is measured using a microwave transmission type molecular orientation meter (for example, MOA-6004, manufactured by Oji Measuring Instruments Co., Ltd.). The angle formed in the biaxial direction is preferably 90 ° ± 5 °, more preferably 90 ° ± 3 °, and even more preferably 90 ° ± 1 °. This film preferably has molecular orientation in the longitudinal direction and the width direction.

(Streak defect area)
In this film, the total area of streaky defect regions observed in the polyester film subjected to the following heat treatment is preferably 40% or less with respect to the total area of the observation region.

In the present disclosure, the "streak defect" means a wrinkle that extends in a streak shape along the longitudinal direction of the film and appears as unevenness in the width direction of the film. As will be described later, since the streak defects occur in the film after production, they are often wrinkles that occur irreversibly. The streak defects do not occur in the heat treatment during the production of the film, but are derived from the wrinkles generated in the heat treatment for the film after the production, and the wrinkles are solidified by cooling after the heat treatment. The "streak defect region" means a portion in the film surface where the streak defect has occurred.
When a streak defect region is generated (that is, a streak defect is partially generated in the film surface), the functional layer formed on the film may have uneven thickness, which may affect the characteristics or appearance of the functional layer. There is sex. Further, streak defect regions tend to be prominent when heated in a state where a tensile load is applied in the longitudinal direction of the film.
On the other hand, when the total area of the streaky defect regions observed after performing the following heat treatment on the biaxially oriented polyester film is less than the above range, the thickness unevenness of the functional layer formed on the film is uneven. Can be reduced.

In this film, the ratio of the total area of streaky defect regions generated when heated at 90 ° C. to the total area of the observation region of the polyester film (hereinafter, also referred to as “area ratio of streak defect regions”) is 40. % Or less is preferable, 30% or less is more preferable, and 18% or less is further preferable. The smaller the value of the area ratio of the streak defect region is, the better, and the lower limit is, for example, 0%.
Further, in this film, the area ratio of the streak defect region generated when heated at 120 ° C. is preferably 90% or less, more preferably 65% or less, still more preferably 40% or less.
When the area ratio of the streak defect region is not more than the above range, the uneven thickness of the functional layer formed on the film can be reduced. The smaller the value of the area ratio of the streak defect region is, the better, and the lower limit is, for example, 0%.
The lower limit of the area ratio of the streak defect region is not particularly limited, but the area ratio of the streak defect region generated when heated at 90 ° C. or 120 ° C. is preferably small, and there is no streak defect region, that is, 0. % Is more preferable.

The area ratio of the streak defect region generated when heated at each temperature of 90 ° C. and 120 ° C. is measured by the following method.
(1) Using a heating and transporting device, heat the polyester film at a surface temperature of 90 ° C. or 120 ° C. while transporting the polyester film under the conditions of a transport speed of 30 m / min and a tension of 100 N / m in the transport direction. The process is performed for 20 seconds. The heating time in the heat treatment is calculated from the time when the surface temperature of the film reaches the target temperature (90 ° C. or 120 ° C.), and the film is heated for 20 consecutive seconds from there. Here, the surface temperature of the film can be measured using a non-contact thermometer (for example, a radiation thermometer). The surface temperature of the film measures whether or not the temperature of the central portion, which is approximately equidistant from both ends in the width direction of the film, has reached the target temperature.
(2) A heat-treated polyester film was placed on a black flat plate, and then a fluorescent lamp installed on the ceiling of the room [For example, Lupica Ace manufactured by Mitsubishi Electric Co., Ltd. (color temperature: 5000K, average color rendering index) ( The polyester film is visually observed from an angle while changing the viewpoint so that the light of Ra): 84)] is reflected. The region where the reflected image of the fluorescent lamp reflected on the surface of the polyester film, which is visually observed, is undulating is defined as a streak defect region.
(3) The number of observed streak defect regions is counted, and the outer circumference of each streak defect region existing in ^{the visually observed observation region (area 1 m 2) of the polyester film is marked.} Next, of the two parallel tangents circumscribing the outer periphery of each streak defect region, the distance between the two parallel tangents selected so as to maximize the distance between the tangents is defined as the length L of the major axis. The distance between two parallel tangents orthogonal to the two parallel tangents giving the length L and circumscribing the outer periphery of the streak defect region is measured with the length S of the minor axis. From the obtained lengths L and S, the area of each streak defect region is calculated by the following formula. From these values, the ratio of the total area of the streak defect region to the total area of the observation region of the polyester film is calculated.
Length of the major axis of the streak defect region L × Length of the minor axis of the streak defect region S × π = Area of the streak defect region The streak defect region may be elliptical or circular as described above. Since there are many, the area of the streak defect region can be calculated by the calculation method of (3) above.

FIG. 1 shows an image (photograph) of a polyester film in which a streak defect region generated by the heat treatment of (1) above is observed. The region surrounded by the solid line shown in FIG. 1 is the streak defect region. In the streak defect region shown in FIG. 1, an uneven shape extending in the transport (MD) direction is observed. The image (photograph) shown in FIG. 1 shows only a part of the observation area.
As described above, the streak defect region is often elliptical or circular. Further, when a streak defect region is generated, at least one elliptical streak defect region whose long axis direction is along the transport direction often appears.

In the biaxially oriented polyester film in which the area ratio of the streak defect region is in the above range, the cooling rate V of the polyester film in the cooling step is 2200 to 3500 ° C./min in the method for producing the polyester film, and the condition 1 described later It can be manufactured by setting the conditions of each process so as to satisfy the above conditions.

(Expansion rate)
The expansion rate of the polyester film in the width direction at 90 ° C. and 120 ° C. is preferably −0.15 to 0.15% with respect to the film width at 30 ° C., respectively, and is −0.10 to 0. It is more preferably 10%, further preferably 0 to 0.10%, and particularly preferably 0 to 0.05%.
By adjusting the expansion coefficient in the width direction of the polyester film at 90 ° C. and 120 ° C. within the above range, not only the expansion in the width direction of the film in the heating process is suppressed, but also the expansion coefficient unevenness at each location on the film surface is reduced. can. As a result, it is presumed that the generation of streaky defect regions due to heating can be suppressed.

The coefficient of expansion in the width direction at each temperature of 90 ° C. and 120 ° C. is measured by the following method using a thermomechanical analyzer.
(1) Prepare a sample adjusted to a size of at least 20 mm in a direction parallel to the width direction of the biaxially oriented film and 4 mm in a direction orthogonal to the width direction of the biaxially oriented film.
(2) Using a thermomechanical analyzer (for example, TMA-60, manufactured by Shimadzu Corporation), a tensile load of 0.1 g is applied to a sample having a width of 4 mm and a length (distance between chucks) of 20 mm.
(3) By raising the temperature of the above sample from a temperature of 20 ° C. or higher and lower than 30 ° C. (preferably 25 ° C.) to 150 ° C. at a heating rate of 5 ° C./min, the dimensional value of the sample at each temperature (° C.) can be adjusted. obtain.
(4) From the sample size at 30 ° C. (L30), the size at 90 ° C. (L90), and the size at 120 ° C. (L120), the expansion coefficient in the width direction at each temperature of 90 ° C. and 120 ° C. using the following formula. Ask for. In the present disclosure, the expansion coefficient in the width direction at 90 ° C. and 120 ° C. is an arithmetic mean value of the expansion coefficient obtained by using five samples, respectively. A positive expansion rate means expansion, and a negative expansion rate means contraction.
Equation: Expansion rate (%) = [(L120 or L90) -L30] / L30 × 100

The ratio (E120 / E90) of the expansion coefficient (E120) in the width direction at 120 ° C. to the expansion coefficient (E90) in the width direction at 90 ° C. is preferably 0 to 1.5, preferably 0 to 1.1. It is more preferably 0 to 1.05, and even more preferably 0 to 1.05. When E120 / E90 is within the above range, uneven thickness of the functional layer can be further suppressed. The coefficient of expansion in the width direction (E90) at 90 ° C. and the coefficient of expansion in the width direction (E120) at 120 ° C. are obtained by the methods using the thermomechanical analyzer described above, respectively.

The expansion rate in the width direction of the polyester film can be adjusted, for example, by appropriately setting the draw ratio in the manufacturing process of the biaxially oriented film, the heat treatment temperature, and the film width during cooling.

(Maximum height of mountain on the surface Rp)
In the polyester film, the maximum mountain height Rp of the particle-containing layer surface is preferably 0.005 μm (5 nm) or more, more preferably 0.01 μm (10 nm) or more, from the viewpoint of further improving the winding quality. In the polyester film, the maximum mountain height Rp of the surface of the particle-containing layer is preferably 1 μm or less, more preferably 0.5 μm or less, and more preferably 0.25 μm (250 nm) in terms of further suppressing transfer failure. It is more preferably 0.2 μm (200 nm) or less, and particularly preferably 0.2 μm (200 nm) or less. In particular, when the particle-containing layer contains inorganic particles, the performance of suppressing transfer failure appears more remarkably, so it is preferable to set the maximum mountain height Rp of the surface of the particle-containing layer within the above range. The maximum mountain height Rp on the surface of the particle-containing layer can be adjusted by adjusting the average particle diameter of the particles of the particle-containing layer and the thickness of the particle-containing layer when the particle-containing layer is formed by in-line coating.

The maximum mountain height Rp of the surface of the polyester film is obtained by cutting out the polyester film to prepare a test piece, measuring the surface of the obtained test piece under the following conditions using the following fine shape measuring device, and then incorporating the test piece. It is obtained by performing particle analysis (multiple levels) with the analysis software used.
The measuring machine and measuring conditions are shown below. In the above measurement, the slice levels are set at equal intervals of 10 nm, the average diameter and density of each slice level are measured 5 times while changing the measurement position, and these average values are calculated to obtain the maximum mountain height Rp. The measured value of. The test piece is fixed to the sample table so that the X direction of the visual field measurement is the width direction of the polyester film.

・ Measuring device: surf-corder ET-4000A manufactured by Kosaka Laboratory
・ Analysis software: i-Face model TDA31 Ver2.2.0.4 JSIS
・ Radius of stylus tip: 0.5 μm
-Measurement field of view: X direction: 380 μm, pitch: 1 μm
Y direction: 280 μm, pitch: 5 μm
・ Needle pressure: 50 μN
・ Measurement speed: 0.1 mm / s
・ Cutoff value: Low range-0.8mm, High range-None ・ Leveling: Whole area ・ Filter: Gaussian filter (2D)
・ Magnification: 100,000 times ・ Particle analysis (multiple levels) conditions ・ Output content setting: Mountain particles ・ Hysteresis width: 5 nm
・ Slice level equal spacing: 10 nm

(density)
The density of the polyester film, in view of more excellent effects of the present invention, preferably 1.39 ~ 1.41g / cm ^3, more preferably ^{1.395 ~ 1.405g / cm 3, 1.398} ~ 1.400g / cm ³ is more preferred.
The density of the polyester film can be measured using an electronic hydrometer (product name "SD-200L", manufactured by Alpha Mirage Co., Ltd.).

(Haze)
When a polyester film is used as a support for a dry film resist, high transparency is required. In particular, higher transparency is required when forming a fine pattern such as a line and space of 50 μm or less. In that respect, the haze of the polyester film is preferably 1% or less, more preferably 0.5% or less, further preferably 0.4% or less, and particularly preferably 0.3% or less. The smaller the haze, the better, so the lower limit of the haze is not limited. If the lower limit of the haze is set for convenience, it is 0% or more. By setting the haze to the above upper limit or less, it is possible to reduce the scattering of ultraviolet rays by the polyester film, which is the support of the resist layer when the resist layer is laminated on the polyester film and then exposed to ultraviolet rays, and after development. It is possible to improve the state of the resist pattern wall surface such as distortion and omission in the patterning of the resist.

Haze is measured by a method according to JIS K7105 using a haze meter (for example, NDH-2000, manufactured by Nippon Denshoku Industries Co., Ltd.).

(B ^* value)
When a polyester film is used as a support for a dry film resist, high transparency is required. In that respect, the ^{b *} ^{value in the L *} a ^* b ^* color system is preferably 0 to 1, more preferably 0 to 0.8, further preferably 0 to 0.6, and particularly preferably 0 to 0.4. preferable. When the ^{b *} value in the ^{L *} a ^* b ^* color system is 0 to 1, the yellowness of the film can be reduced, so that the hue of the film can be made almost colorless. As a result, the polyester film can be preferably applied, for example, in applications where high visibility is required (for example, a display device).

^{The b *} value in the L ^* a ^* b ^* color system is measured by a transmission method using a spectral color difference meter (for example, SE-2000, manufactured by Nippon Denshoku Industries Co., Ltd.).

(thickness)
The thickness of the polyester film is preferably 100 μm or less, more preferably less than 50 μm, still more preferably 40 μm or less, in that an increase in haze value can be suppressed and laminating suitability can be improved. The lower limit of the thickness is not particularly limited, but 3 μm or more is preferable, 5 μm or more is more preferable, and 10 μm or more is further preferable, in terms of improving the strength and the workability.
The thickness of the polyester film is an arithmetic mean value of the thickness of five points measured by a scanning electron microscope (SEM).

〔Production method〕
Examples of the method for producing this film include a method of biaxially stretching an unstretched polyester film.

The biaxial stretching may be simultaneous biaxial stretching in which longitudinal stretching and transverse stretching are performed at the same time, or sequential biaxial stretching in which longitudinal stretching and transverse stretching are divided into two or more stages. Examples of the form of sequential biaxial stretching include longitudinal stretching → transverse stretching, longitudinal stretching → transverse stretching → longitudinal stretching, longitudinal stretching → longitudinal stretching → transverse stretching, and transverse stretching → longitudinal stretching, longitudinal stretching → transverse stretching. Is preferable.

<Stretching machine>
The apparatus used for biaxial stretching is not particularly limited, and a known stretching machine can be used. Hereinafter, an example of the stretching machine will be described with reference to the drawings.

FIG. 2 is a plan view showing an example of a stretching machine used for manufacturing a polyester film.
The stretching machine 100 shown in FIG. 2 includes a pair of

annular rails

60a and 60b, and gripping members 2a to 2l attached to each annular rail and movable along the rails. The

annular rails

60a and 60b are arranged symmetrically with respect to each other with the film 200 interposed therebetween. The stretching machine 100 can stretch the film 200 in the width direction by gripping the film 200 with the gripping members 2a to 2l and moving the gripping members 2a to 2l along the rail.

The stretching machine 100 has a region including a preheating section 10, a stretching section 20, a heat fixing section 30, a heat relaxing section 40, and a cooling section 50 in this order from the upstream side in the transport direction.
The above-mentioned region of the stretching machine 100 is divided by a windbreak curtain, and the temperature in the region can be individually adjusted by hot air or the like.

The preheating unit 10 is a region for preheating the film 200.

The stretched portion 20 is a region in which the preheated film 200 is stretched by applying tension in the direction of the arrow TD (width direction), which is a direction orthogonal to the direction of the arrow MD (longitudinal direction). As shown in FIG. 2, in the stretched portion 20, the film 200 is stretched from the width L0 to the width L1.

The heat fixing portion 30 is a region where the film 200 to which tension is applied is heated and heat-fixed while being tensioned.

The heat relaxation unit 40 is a region for heat-relaxing the tension of the heat-fixed film 200 by heating the heat-fixed film 200.
As shown in FIG. 2, in the heat relaxation unit 40, the film 200 is reduced (relaxed) from the width L1 to the width L2.

The cooling unit 50 is a region for cooling the heat-relaxed film 200. By cooling the film 200, the shape of the film 200 can be fixed.
FIG. 2 shows that the width of the film 200 carried into the cooling unit 50 is L2, and the width of the film 200 carried out from the cooling unit 50 is L3.

The annular rail 60a is attached with gripping

members

2a, 2b, 2e, 2f, 2i, and 2j that are movable along the annular rail 60a. The annular rail 60b is attached with gripping

members

2c, 2d, 2g, 2h, 2k, and 2l that are movable along the annular rail 60b.
The gripping

members

2a, 2b, 2e, 2f, 2i, and 2j grip one end of the film 200 in the direction of the arrow TD. The gripping

members

2c, 2d, 2g, 2h, 2k, and 2l grip the other end of the film 200 in the direction of the arrow TD. The gripping members 2a to 2l are often referred to as chucks, clips, or the like.
The gripping

members

2a, 2b, 2e, 2f, 2i, and 2j move counterclockwise along the annular rail 60a. The gripping

members

2c, 2d, 2g, 2h, 2k, and 2l move clockwise along the annular rail 60b.

The gripping members 2a to 2d move along the

annular rail

60a or 60b while gripping the end portion of the film 200 in the preheating portion 10, pass through the stretching portion 20, the heat fixing portion 30, and the heat relaxing portion 40, and then the cooling portion. Proceed to 50. Next, the gripping

members

2a and 2b and the gripping

members

2c and 2d are end portions on the downstream side in the direction of the arrow MD of the cooling unit 50 (for example, the gripping release point P and the grip release point Q in FIG. 2) in the order of transport direction. After separating the end portion of the film 200 at), the film further moves along the

annular rail

60a or 60b and returns to the preheating portion 10. In the above process, by moving the film 200 in the direction of the arrow MD, preheating in the preheating section 10, stretching in the stretching section 20, heat fixing in the heat fixing section 30, heat relaxation in the heat relaxing section 40, And cooling is performed by the cooling unit 50, and the film is laterally stretched.

By adjusting the moving speed of the gripping members 2a to 2l, the transport speed of the film 200 can be adjusted. Further, the gripping members 2a to 2l can independently change the moving speed.

As described above, the stretching machine 100 enables lateral stretching in the stretching portion 20 to stretch the film 200 in the direction of the arrow TD. On the other hand, the stretching machine 100 can also stretch the film 200 in the direction of the arrow MD by changing the moving speed of the gripping members 2a to 2l. That is, it is also possible to perform simultaneous biaxial stretching using the stretching machine 100.

The stretching machine 100 may further have other gripping members in addition to the gripping members 2a to 2l in order to support the film 200 (not shown).

Next, a method for producing a polyester film according to an example of the embodiment of the present invention (hereinafter, also referred to as "the present production method") will be specifically described.

This manufacturing method is a method for manufacturing a biaxially oriented polyester film, which includes an extrusion molding step of extruding a molten resin containing a raw material polyester into a film to form an unstretched polyester film containing at least a polyester base material, and a non-extrusion molding step. A longitudinal stretching step of stretching a stretched polyester film in a transport direction to form a uniaxially oriented polyester film, a transverse stretching step of stretching a uniaxially oriented polyester film in the width direction to form a biaxially oriented polyester film, and a biaxially oriented polyester film. A heat fixing step that heats and fixes the oriented polyester film, a heat relaxation step that heats the heat-fixed polyester film at a temperature lower than that of the heat fixing step to relieve heat, and a heat relaxation step that heats the film. It has a cooling step of cooling the relaxed polyester film and an expansion step of expanding the heat-relaxed polyester film in the width direction in the cooling step.
The present production method further includes a particle-containing layer forming step of providing a particle-containing layer containing particles on at least one surface of the polyester base material.

<Extrusion molding process>
The extrusion molding step is a step of extruding a molten resin containing polyester as a raw material into a film by an extrusion molding method to form an unstretched polyester film. The raw material polyester has the same meaning as the polyester described in the above item (polyester). The unstretched polyester film formed by the extrusion molding step contains at least a polyester substrate.

The extrusion molding method is a method of molding a raw material resin into a desired shape by extruding a melt of the raw material resin using, for example, an extruder.
For the molten resin containing polyester, for example, using an extruder equipped with one or more screws, the polyester described above is heated to a temperature equal to or higher than the melting point, and the screw is rotated to melt and knead. Is formed by. Polyester is melted in an extruder by heating and kneading with a screw to form a melt.

The melt is extruded from the extrusion die through a gear pump, a filter, etc. The extrusion die is also simply referred to as a "die" (see JIS B8650: 2006, a, extruder, number 134). For example, the extrusion die described in JP-A-2005-297266, the extrusion die described in JP-A-1-154720, and a combination thereof can also be used. The melt may be extruded in a single layer or in multiple layers.

In melt extrusion, it is preferable to replace the inside of the extruder with nitrogen from the viewpoint of suppressing thermal decomposition (for example, hydrolysis of polyester) in the extruder. Further, the extruder is preferably a twin-screw extruder because the kneading temperature can be kept low.

The melt extruded from the extrusion die is cooled to form a film. For example, the melt can be formed into a film by bringing the melt into contact with a casting roll and cooling and solidifying the melt on the casting roll. In cooling the melt, it is more preferable to blow wind (preferably cold air) on the melt.

The temperature of the casting roll is preferably more than (Tg-10) ° C. and (Tg + 30) ° C., more preferably (Tg-7) to (Tg + 20) ° C., and even more preferably (Tg-5) to (Tg + 10) ° C. The above-mentioned "Tg" means the glass transition temperature of the polyester constituting the film.
Here, the temperature of the polyester film and each member in the present manufacturing method can be measured by using a non-contact thermometer (for example, a radiation thermometer). The surface temperature of the film is obtained by measuring the temperature of the central portion in the width direction of the film five times and calculating the average value of the obtained measured values.

When a casting roll is used in the extrusion molding process, it is preferable to improve the adhesion between the casting roll and the melt. Examples of the method for improving the adhesion include an electrostatic application method, an air knife method, an air chamber method, a vacuum nozzle method, and a touch roll method.

The molded product (unstretched polyester film) cooled using a casting roll or the like is stripped from the cooling member such as a casting roll by using a stripping member such as a stripping roll.

<Vertical stretching process>
The longitudinal stretching step is a step of stretching an unstretched polyester film in the transport direction (hereinafter, also referred to as “longitudinal stretching”). A uniaxially oriented polyester film is formed by the longitudinal stretching step.

In the longitudinal stretching step, it is preferable to preheat the unstretched polyester film before longitudinal stretching. By preheating the unstretched polyester film, the polyester film can be easily stretched vertically.
The preheating temperature of the unstretched polyester film is preferably (Tg-30) to (Tg + 40) ° C, more preferably (Tg-20) to (Tg + 30) ° C. Specifically, the preheating temperature is preferably 60 to 100 ° C, more preferably 65 to 80 ° C.
As a method for preheating the unstretched polyester film, for example, a method of arranging a preheating roll having a function of preheating the film on the upstream side of the vertically stretched stretch roll and preheating while transporting the unstretched polyester film can be mentioned. Be done.

Further, the stretched roll may have a function of preheating the film. The preferable range of the preheating temperature of the film by the stretch roll is the same as the preferable range of the preheating temperature of the preheating roll described above.

Longitudinal stretching can be performed, for example, by applying tension between two or more pairs of stretch rolls installed in the transport direction while transporting the unstretched polyester film in the longitudinal direction. For example, when a pair of stretched rolls A and a pair of stretched rolls B are installed on the upstream side in the transport direction, the rotation speed of the stretched rolls B is set when the unstretched polyester film is transported. By increasing the rotation speed of A, the unstretched polyester film is stretched in the longitudinal direction.

In the longitudinal stretching step, the transport speed (peripheral speed) of the film by the pair of stretch rolls A provided on the upstream side in the transport direction and the pair of stretch rolls B provided on the downstream side in the transport direction is the film by the stretch roll A. The transport speed of the film is not particularly limited as long as it is slower than the transport speed of the film by the stretch roll B.
The transport speed of the film by the stretch roll A is, for example, 5 to 60 m / min, preferably 10 to 50 m / min, and more preferably 15 to 45 m / min. The transport speed of the film by the stretch roll B is, for example, 40 to 160 m / min, preferably 50 to 150 m / min, and more preferably 60 to 140 m / min.

The draw ratio in the longitudinal stretching step is appropriately set depending on the application, but is preferably 2.0 to 5.0 times, more preferably 2.5 to 4.0 times, still more preferably 2.8 to 4.0 times. ..

The stretching speed in the longitudinal stretching step is preferably 800 to 1500% / sec, more preferably 1000 to 1400% / sec, and even more preferably 1200 to 1400% / sec. Here, the "stretching speed" is a value obtained by dividing the length Δd in the transport direction of the polyester film stretched in 1 second in the longitudinal stretching step by the length d0 in the transport direction of the polyester film before stretching as a percentage. It is a value expressed by.

In the longitudinal stretching step, it is preferable to heat the unstretched polyester film. This is because longitudinal stretching becomes easier by heating.
The heating temperature in the longitudinal stretching step is preferably (Tg-20) to (Tg + 50) ° C, more preferably (Tg-10) to (Tg + 40) ° C, and even more preferably (Tg) to (Tg + 30) ° C. Specifically, the heating temperature in the longitudinal stretching step is preferably 70 to 120 ° C, more preferably 80 to 110 ° C, and even more preferably 85 to 100 ° C.

Examples of the method of heating the unstretched polyester film in the longitudinal stretching step include a method of heating a roll such as a stretched roll in contact with the unstretched polyester film. Examples of the method of heating the roll include a method of providing a heater inside the roll and a method of providing a pipe inside the roll and allowing the heated fluid to flow in the pipe. In addition to the above, for example, a method of applying warm air to the unstretched polyester film, and heating the unstretched polyester film by bringing the unstretched polyester film into contact with a heat source such as a heater or passing it in the vicinity of the heat source. The method can be mentioned.

The longitudinal stretching step of longitudinally stretching the unstretched polyester film is not limited to the above method.
In the above-mentioned longitudinal stretching step, the unstretched polyester film is longitudinally stretched by utilizing the difference in the transport speeds of the two stretched rolls, but it is arranged between the two stretched rolls and is faster than those stretched rolls. A uniaxially oriented polyester film may be produced by longitudinally stretching an unstretched polyester film using one or more high-speed stretching rolls that transport the film at a transport speed.
Further, in the above-mentioned longitudinal stretching step, the film is sandwiched and conveyed by two rolls (a pair of rolls) facing each other, but the stretching rolls used in the longitudinal stretching step have the opposing rolls. It may be composed of only one roll in contact with one surface of the polyester film.

<Transverse stretching process>
The transverse stretching step is a step of transversely stretching a uniaxially oriented polyester film. The transverse stretching step is carried out, for example, in the transverse stretching portion 20 of the stretching machine 100.

In the transverse stretching step, it is preferable to preheat the polyester film before the transverse stretching. By preheating the polyester film, the polyester film can be easily stretched laterally.
The preheating temperature is preferably (Tg-10) to (Tg + 60) ° C, more preferably (Tg) to (Tg + 50) ° C. Specifically, the preheating temperature is preferably 80 to 120 ° C, more preferably 90 to 110 ° C.

The stretching ratio in the width direction (transverse stretching ratio a) of the uniaxially oriented polyester film in the transverse stretching step is not particularly limited, but is preferably larger than the stretching ratio in the longitudinal stretching step. The stretching ratio a in the transverse stretching step is preferably 3.0 to 6.0 times, more preferably 3.5 to 5.0 times, still more preferably 3.5 to 4.5 times.
When the transverse stretching step is carried out in the transverse stretching portion 20 of the stretching machine 100, the transverse stretching ratio a is the ratio of the film width L1 at the time of carrying out from the transverse stretching portion 20 to the film width L0 at the time of carrying in the transverse stretching portion 20. It is obtained from L1 / L0).

The area magnification represented by the product of the stretching ratio in the longitudinal stretching step and the stretching ratio in the transverse stretching step is preferably 12.8 to 15.5 times, more preferably 13.5 to 15.2 times, and 14. It is more preferably 0 to 15.0 times. When the area magnification is at least the above lower limit value, the molecular orientation in the film width direction becomes good. Further, when the area magnification is not more than the above upper limit value, it is easy to maintain a state in which the molecular orientation is difficult to be relaxed when subjected to the heat treatment.

The heating temperature in the transverse stretching step is preferably (Tg-10) to (Tg + 80) ° C, more preferably (Tg) to (Tg + 70) ° C, and even more preferably (Tg) to (Tg + 60) ° C. Specifically, the heating temperature in the transverse stretching step is preferably 100 to 140 ° C, more preferably 110 to 135 ° C, and even more preferably 115 to 130 ° C.

The stretching speed in the transverse stretching step is preferably 8 to 45% / sec, more preferably 10 to 30% / sec, and even more preferably 15 to 20% / sec.

<Heat fixing process>
In this production method, a heat fixing step and a heat relaxation step are performed as heat treatment for the polyester film laterally stretched by the transverse stretching step.
In the heat fixing step, the biaxially oriented polyester film obtained by the transverse stretching step is heated and heat-fixed. By crystallizing the polyester by heat fixing, shrinkage of the polyester film can be suppressed.
The heat fixing step is carried out, for example, in the heat fixing portion 30 of the stretching machine 100.

The surface temperature (heat fixing temperature T1) of the polyester film in the heat fixing step is preferably 190 to 240 ° C., more preferably 200 to 240 ° C., and even more preferably 210 to 230 ° C.
In the heat fixing step, the heat treatment is performed while controlling the maximum temperature reached on the surface of the polyester film to be the heat fixing temperature T1.

In the heat fixing step, the variation in the surface temperature in the film width direction is preferably 0.5 to 10.0 ° C, more preferably 0.5 to 7.0 ° C, still more preferably 0.5 to 5.0 ° C. 0.5 to 4.0 ° C. is particularly preferable. By controlling the variation in the surface temperature in the film width direction within the above range, the variation in the crystallinity in the width direction can be suppressed.

Examples of the heating method include a method of applying hot air to the film and a method of radiant heating of the film. Examples of the device used in the method of radiant heating include an infrared heater.

The heating time in the heat fixing step is preferably 5 to 50 seconds, more preferably 5 to 30 seconds, and even more preferably 5 to 10 seconds.

<Heat relaxation process>
In the heat relaxation step, the polyester film heat-fixed by the heat-fixing step is heated at a temperature lower than that of the heat-fixing step to heat-relax. Residual strain of the polyester film can be alleviated by heat relaxation.
The heat relaxation step is carried out, for example, in the heat relaxation unit 40 of the stretching machine 100.

The surface temperature (heat relaxation temperature T2) of the polyester film in the heat relaxation step is preferably 5 ° C. or higher lower than the heat fixation temperature T1, more preferably 15 ° C. or higher, further preferably 25 ° C. or higher, and 30. Temperatures as low as ° C. or higher are particularly preferred. That is, the heat relaxation temperature T2 is preferably 235 ° C or lower, more preferably 225 ° C or lower, further preferably 210 ° C or lower, and particularly preferably 200 ° C or lower.
The lower limit of the heat relaxation temperature T2 is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, still more preferably 120 ° C. or higher.
In the heat relaxation step, the heat treatment is performed while controlling the maximum temperature reached on the surface of the polyester film to be the heat relaxation temperature T2.

<Cooling process>
The manufacturing method comprises a cooling step of cooling the heat-relaxed polyester film. The cooling step and the expansion step described later are carried out, for example, in the cooling unit 50 of the stretching machine 100.

Examples of the method for cooling the polyester film in the cooling step include a method of blowing air (preferably cold air) on the film and a method of bringing the film into contact with a temperature-adjustable member (for example, a temperature control roll).
The cooling temperature in the cooling step is preferably 130 ° C. or lower in order to distinguish it from the heat relaxation step. The cooling temperature is more preferably 30 to 120 ° C, further preferably 30 to 100 ° C, and particularly preferably 30 to 80 ° C.

In this manufacturing method, the cooling step is carried out so that the cooling rate V of the polyester film is 2200 to 3500 ° C./min. By adjusting the cooling rate V within the above range, it is possible to reduce the thickness unevenness of the functional layer laminated on the biaxially oriented film.
Although the details of the mechanism by which the thickness unevenness of the functional layer is reduced by specifying the range of the cooling rate V are not clear, the cooling that can efficiently lower the temperature of the film surface and suppress the temperature unevenness of the film surface. It is presumed that by setting the speed, the strain inherent in the film after cooling can be reduced, and the generation of waviness due to the high temperature treatment at the time of laminating the functional layer can be suppressed.
From the above viewpoint, the cooling rate V in the cooling step is preferably 2200 to 3000 ° C./min, more preferably 2300 to 2600 ° C./min.

The cooling rate V of the polyester film in the cooling step can be measured using a non-contact thermometer. For example, when the cooling step is carried out in the cooling unit 50 of the stretching machine 100, the surface temperature of the film 200 carried from the heat relaxation unit 40 to the cooling unit 50 and the surface temperature of the film 200 carried out from the cooling unit 50 Is measured to obtain the temperature difference ΔT (° C.) between the two. The cooling rate V is obtained by dividing the obtained temperature difference ΔT (° C.) by the residence time ta of the film 200 in the cooling unit 50.
The cooling speed of the polyester film can be adjusted by the operating conditions of the cooling device and the transport speed of the film.

It is preferable that the above-mentioned heat fixing step, heat relaxation step and cooling step in this manufacturing method are continuously carried out in this order. This is because the load (heat history) due to repeated heating and cooling of the polyester film can be reduced, the strain inherent in the film can be reduced, and the occurrence of streak defects can be suppressed.

<Expansion process>
The present manufacturing method has an expansion step of expanding the heat-relaxed polyester film in the width direction in the cooling step.
"Expanding the polyester film in the width direction" in the cooling step means the film width at the end of the cooling step (L2 in FIG. 2) rather than the film width of the polyester film at the start of the cooling step (L2 in FIG. 2). It means applying tension in the width direction to the polyester film during the cooling step so that L3) becomes wider.

In the cooling step, the method of expanding the polyester film in the width direction is not particularly limited. For example, when a biaxially oriented polyester film is manufactured using the above-mentioned stretching machine 100, the end point of the cooling unit 50 (grasping release point P and gripping release point P) is more than the distance between the

annular rails

60a and 60b at the start point of the cooling unit 50. By increasing the distance between the

annular rails

60a and 60b at the release point Q), the film 200 gripped by each gripping member can be expanded in the width direction in the cooling step.
The expansion step may be carried out continuously or intermittently from the start to the end of the cooling step as long as the film width is expanded before and after the cooling step, or may be carried out only at one time during the cooling step.
The expansion step is preferably performed at 130 ° C. or lower. Among them, 30 to 120 ° C. is more preferable, 30 to 100 ° C. is further preferable, and 30 to 80 ° C. is particularly preferable.

The expansion ratio in the width direction of the polyester film by the expansion step, that is, the ratio of the film width at the end of the cooling step to the film width before the start of the cooling step is not particularly limited as long as it is larger than 0, but the effect of the present invention is effective. From a more excellent point, the percentage b of the expansion rate is preferably 0.001% or more, and more preferably 0.01% or more.
The upper limit is not particularly limited, but the percentage b of the expansion rate is preferably 1.3% or less, more preferably 1.2% or less, and further preferably 1.0% or less. When a strong tension is applied in the transport direction in order to transport the film at high speed by setting the expansion rate of the film width to the above upper limit value or less (for example, when the tension in the transport direction is 100 N / m or more). ), It is possible to suppress the disorder of the cut surface in the trimming step described later, and further, the breakage of the film due to the cutting disorder.

<Particle-containing layer forming process>
The present production method includes a particle-containing layer forming step of providing a particle-containing layer on at least one surface of a polyester base material. The particle-containing layer formed by the particle-containing layer forming step has the same meaning as the particle-containing layer described in detail in the above item <Particle-containing layer>.
The formation of the particle-containing layer may be performed at any stage of the present production method, for example, at least one of the unstretched or stretched polyester base materials using a coating liquid containing the material constituting the particle-containing layer. Examples thereof include a method of forming a coating film on the surface of the polyester and drying it if necessary, and a method of forming a particle-containing layer at the same time as forming a polyester base material by a coextrusion method.

First, a method of forming a particle-containing layer using a coating liquid for a particle-containing layer will be described.
The coating liquid for the particle-containing layer can be prepared by mixing the particles contained in the particle-containing layer, the binder and additives added as necessary, and the solvent. Examples of the solvent include water, ethanol, toluene, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, propylene glycol monomethyl ether and propylene glycol monoethyl ether. Of these, water is preferable from the viewpoint of environment, safety and economy.

The coating liquid for a particle-containing layer may contain one type of solvent alone, or may contain two or more types of solvents.
The content of the solvent is preferably 80 to 99% by mass, more preferably 90 to 98% by mass, based on the total mass of the coating liquid for the particle-containing layer.
That is, the total content of the components (solid content) other than the solvent in the coating liquid for the particle-containing layer is preferably 0.5 to 20% by mass, preferably 1 to 10% by mass, based on the total mass of the coating liquid for the particle-containing layer. More preferably by mass.
The components other than the solvent in the coating liquid for the particle-containing layer are the same as those described for each component contained in the particle-containing layer, including the preferred embodiment thereof. Further, the content of each component in the coating liquid is such that the content of each component with respect to the total mass of the solid content of the coating liquid for the particle-containing layer is the same as the preferable content of each component with respect to the total mass of the particle-containing layer described above. It is preferable to adjust the amount.
The average particle size of the particles contained in the coating liquid for the particle-containing layer is measured using a laser diffraction / scattering type particle size distribution measuring device (“LA-950”, manufactured by HORIBA, Ltd.). When a commercially available particle product is used, the average particle size of the particles may be a catalog value.

The coating method of the coating liquid for the particle-containing layer is not particularly limited, and a known method can be used. Examples of the coating method include a spray coating method, a slit coating method, a roll coating method, a blade coating method, a spin coating method, a bar coating method and a dip coating method.

As a method for forming the particle-containing layer using the coating liquid for the particle-containing layer, a so-called in-line coating method in which the coating liquid is applied to the surface of at least one of the polyester base materials while transporting the polyester base material, and biaxial Any of the so-called offline coating methods in which a coating liquid is separately applied after producing the oriented polyester base material can be applied, but the in-line coating method is preferable in terms of higher efficiency and imparting transparency. ..
In the in-line coating method, the polyester base material to which the coating liquid for the particle-containing layer is applied may be an unstretched polyester base material or a uniaxially oriented polyester base material, but may be uniaxially oriented. It is preferably a polyester base material.

Next, a method of forming the particle-containing layer at the same time as forming the polyester base material by the coextrusion method will be described.
The method for forming the particle-containing layer by the coextrusion method is not particularly limited. For example, a resin composition containing the particles and binders constituting the particle-containing layer and additives added as needed is prepared and obtained according to the method described in the above <Extrusion molding step>. A particle-containing layer can be formed by heating and melt-kneading the resin composition to prepare a melt of the resin composition and extruding it together with the melt of polyester using an extruder.

In the particle-containing layer forming step, the heating time of the polyester base material in the manufacturing process can be shortened, and the strain inside the polyester base material can be reduced. The in-line coating step of forming the particle-containing layer using the polyester base material, or the polyester base material using the first melt containing polyester and the second melt containing particles and the binder constituting the polyester base material. It is preferably a coextrusion molding step of forming the particle-containing layer at the same time.
Above all, it is preferable to apply the above-mentioned in-line coating method to the uniaxially oriented polyester base material between the longitudinal stretching step and the transverse stretching step to form a particle-containing layer. A coating liquid for a particle-containing layer is applied to at least one surface of a uniaxially oriented polyester base material to form a particle-containing layer, and then the polyester base material and the particle-containing layer are simultaneously transversely stretched to form a polyester group. The adhesion of the material and the particle-containing layer can be improved. The specific method of lateral stretching at that time is as described in the above-mentioned transverse stretching step.

The present manufacturing method may include a winding step of obtaining a roll-shaped biaxially oriented polyester film by winding the biaxially oriented polyester film obtained through the above steps.
Further, the present manufacturing method further includes a trimming step of continuously cutting the polyester film along the transport direction and cutting off at least one end in the width direction of the polyester film before carrying out the winding step. You may.

<Manufacturing conditions>
This manufacturing method satisfies the following condition 1.
Condition 1: The melting point of the polyester constituting the polyester substrate is Tm (° C), the heat fixing temperature in the heat fixing step is T1 (° C), the draw ratio of the uniaxially oriented polyester film in the transverse stretching step is a, and the heat in the expansion step. When the percentage of the expansion rate in the width direction of the relaxed polyester film is b (%), the product of A calculated by the following formula (1) and B calculated by the following formula (2) (A × B). ) Is a value C of -4.0 to 4.0. However, this excludes cases where only one of A and B is 0.
A = Tm-T1-30 (1)
B = a / 5-b (2)

Although the details of the mechanism by which the thickness unevenness of the functional layer is reduced by setting the conditions of each step so as to satisfy the above condition 1, the details of the mechanism are not clear, but the excessive crystallization of polyester in the heat fixing step is suppressed and the polyester is not excessively crystallized. By expanding in the width direction at a predetermined expansion rate in the cooling process, the abundance ratio of the polyester molecular chains oriented in the width direction increases, thereby reducing the dimensional change rate due to heating in the subsequent process, and as a result, the function. It is presumed that this is because the generation of waviness due to high temperature treatment in the process of laminating layers can be suppressed.
From the above viewpoint, the absolute value of the above value C is preferably 0.1 to 0.7, and more preferably the above value C is 0.1 to 0.5.
As described above, if only one of A and B is 0, the condition 1 is not satisfied, but if both A and B are 0, the condition 1 is satisfied.

In this production method, the melting point of the polyester constituting the polyester base material is Tm (° C.), the heat fixing temperature in the heat fixing step is T1 (° C.), and the stretching ratio of the uniaxially oriented polyester film in the transverse stretching step is a. When the percentage of the expansion rate in the width direction of the heat-relaxed polyester film in the expansion step is b (%) and the cooling rate in the cooling step is V (° C./min), A, calculated by the above formula (1). It is preferable that B calculated by the above formula (2) and D calculated from the following formula (3) from the cooling rate V are 1 to 10000.
D = (A x B) ² x V (3)

Although the details of the mechanism for reducing the thickness unevenness of the functional layer by setting the conditions of each step so that the above value D is within the above range are not clear, the above range and value of the cooling rate V are not clear. A mechanism similar to the mechanism in which the thickness unevenness is reduced by specifying the range of C is presumed.
The above value D is preferably 0.1 to 6000, more preferably 1 to 1500, from the above viewpoint.

The transport speed of the polyester film in each step other than the longitudinal stretching step of this production method is not particularly limited, but the transverse stretching step, the heat fixing step, the heat relaxation step, the cooling step and the expansion step are performed by using the stretching machine 100. In this case, the transport speed of the polyester film is preferably 50 to 200 m / min, more preferably 80 to 150 m / min in terms of productivity and quality. Further, the transport speed of the polyester film from the cooling step to the winding in the above winding step is preferably 50 to 200 m / min, more preferably 80 to 150 m / min. The transport speed of the polyester film in the longitudinal stretching step is as described above.

Further, in each step other than the longitudinal stretching step, the tension applied to the polyester film in the transport direction is not particularly limited, but the transverse stretching step, the heat fixing step, the heat relaxation step, the cooling step and the expansion step are performed on the stretching machine 100. The tension applied to the polyester film in the transport direction can be adjusted by the stretching conditions.
Further, the tension applied to the polyester film in the transport direction after the cooling step is applied until the polyester film is taken up in the above winding step is preferably 3 to 30 N / m, more preferably 5 to 20 N / m.

[Laminated film]
The use of this film is not particularly limited, but it is preferable to further laminate functional layers to produce a laminated film.
Examples of the functional layer laminated on this film include a decorative layer, a photosensitive resin layer, a magnetic layer, a peeling layer, an adhesive layer, a conductive layer, a refractive index adjusting layer, and a visibility layer.
As a laminated film, in order to maintain slipperiness (transportability) due to the particle-containing layer, the particle-containing layer is provided only on one surface of the polyester base material, and is opposite to the particle-containing layer of the polyester base material. It is preferable that the functional layer is provided on the surface on the side.

More specific examples of the laminated film include a decorative film whose functional layer is a decorative layer, a photosensitive transfer film whose functional layer is a photosensitive resin layer and used as a support for a dry film resist, and a functional layer. A release film that is a release layer (protective film for dry film resist, release film for ceramic green sheet production, release film for semiconductor process production), adhesive film whose functional layer is an adhesive layer (adhesive film for semiconductor process production), functional layer Is a transparent conductive substrate film, the functional layer is a photosensitive resin layer, a photosensitive transfer film for forming an etching resist film, which is a visibility layer, and the functional layer is a photosensitive resin layer and a refractive index adjusting layer. Examples thereof include a photosensitive transfer film for forming a protective film for a touch panel.

The method of laminating the functional layer on the surface of this film is not particularly limited, but it is preferable to apply a coating liquid containing the material constituting the functional layer to the surface of the biaxially oriented polyester film to form the functional layer, and the productivity is preferable. It is more preferable to form the functional layer by applying the coating liquid for the functional layer to the surface of the present film and then heating the coating film while transporting the present film.
This film can suppress the generation of streaky defect regions in the biaxially oriented polyester film and suppress the uneven thickness of the laminated functional layer even when the heat treatment is performed in the process of forming the functional layer. ..

The laminated film may have a layer other than the present film and the functional layer. Examples of the layer other than the present film and the functional layer include a base layer containing a binder resin provided for the purpose of improving the adhesion between the present film and the functional layer.

It is preferable to apply this film as a support for a dry film resist. As the functional layer, a photosensitive resin layer may be provided, and a decorative layer, a refractive index adjusting layer, and / or a visible layer may be further laminated. When there are a plurality of functional layers, they tend to be heated each time they are laminated and uneven thickness tends to occur. However, by using this film, the problem of uneven thickness can be solved.
The photosensitive resin layer is not particularly limited, but is preferably a negative type. Specifically, the binder polymer, ethylenically unsaturated compound, or photopolymerization initiator described in International Publication No. 2018/105313 can be mentioned as a preferable form. The photosensitive resin layer is more preferably a layer having an alkali-soluble acrylic resin having a cyclic structure, a polyfunctional acrylate, and an oxime-based photopolymerization initiator or a bisimidazole-type photopolymerization initiator.

In the case of a dry film resist support for forming an electrode protective film for a touch panel, it is preferable that a refractive index adjusting layer is laminated separately from the photosensitive resin layer. Preferred forms of the refractive index adjusting layer include the second curable transparent resin layer described in JP-A-2014-108541. The refractive index of the refractive index adjusting layer is preferably 1.6 or more, and the refractive index adjusting layer preferably has metal oxide particles having a high refractive index such as titanium oxide and zirconium oxide.

In the case of a dry film resist support for forming a decorative pattern, it is preferable that the photosensitive resin layer is colored. The colored photosensitive resin layer is preferably formed from the photosensitive resin composition described in International Publication No. 2017/208849. The colored photosensitive resin layer is preferably a layer having a pigment as a colorant, and more preferably a layer having a pigment, a binder polymer, a polyfunctional acrylate, and a photopolymerization initiator.

In the case of a dry film resist support for forming an etching resist used for forming a fine pattern of 50 μm or less, it is preferable that a visibility layer is laminated separately from the photosensitive resin layer. Since there is a visibility layer, it can be visually recognized in the process of confirming the pattern latent image.

It is also preferable to apply this film as a release film for producing a ceramic green sheet. In the case of a release film, a release layer is often provided as a functional layer. A preferred form of the release layer is a layer having a silicone resin.

The present disclosure will be described in more detail with reference to examples below. The materials, amounts, ratios, treatment contents, and treatment procedures shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present disclosure. Therefore, the scope of the present disclosure is not limited to the specific examples shown below. Unless otherwise specified, "parts" and "%" are based on mass.

Hereinafter, in the present embodiment, the term "film" includes both a polyester base material alone and an embodiment having a polyester base material and a particle-containing layer, and an unstretched film, a uniaxially oriented film, and the like. And all of the biaxially oriented films shall be included.
Further, in each step of this embodiment, a non-contact thermometer (AD-5616 (product name), manufactured by A & D Co., Ltd., emissivity 0.95) is used to measure the temperature of the central portion in the width direction of the film five times. Then, the arithmetic mean value of the obtained measured values was used as the measured value of the surface temperature of the film.

[Example 1]
<Extrusion molding process>
Pellets of polyethylene terephthalate were produced using a titanium compound (citrate chelated titanium complex, VERTEC AC-420, manufactured by Johnson Matthey) described in Japanese Patent No. 5575671 as a polymerization catalyst. Specifically, 1 ton (1000 kg) of terephthalic acid, 390 kg of ethylene glycol, and 9 mass ppm of Ti atom with respect to polyethylene terephthalate produced as a titanium compound were mixed. The obtained mixture was continuously supplied to the reactor to carry out an esterification reaction. Further, magnesium acetate tetrahydrate in an amount of 81 mass ppm of Mg atom with respect to the produced polyethylene terephthalate and trimethyl phosphate in an amount of 73 mass ppm of P atom with respect to the produced polyethylene terephthalate. Was added to the mixture and a polycondensation reaction was carried out to produce pellets of polyethylene terephthalate.
The obtained pellets were dried to a water content of 50 ppm or less, charged into a hopper of a uniaxial kneading extruder having a diameter of 30 mm, and then melted and extruded at 280 ° C. The melt was passed through a filter (pore diameter 3 μm) and then extruded from the die into a cooling drum at 25 ° C. to obtain an unstretched film made of polyethylene terephthalate. The extruded melt was brought into close contact with the cooling drum by the electrostatic application method.
The melting point (Tm) of polyethylene terephthalate constituting the unstretched film was 258 ° C., and the glass transition temperature (Tg) was 80 ° C.

<Vertical stretching process>
The unstretched film was subjected to a longitudinal stretching step by the following method.
A uniaxially oriented film was produced by passing a preheated unstretched film between two pairs of rolls having different peripheral speeds and stretching the film in the vertical direction (conveyance direction) under the following conditions.
(Vertical stretching conditions)
Preheating temperature: 75 ° C
Stretching temperature: 90 ° C
Stretching ratio: 3.4 times Stretching speed: 1300% / sec

<Particle-containing layer forming process>
The following coating liquid for a particle-containing layer is applied to one side of a vertically stretched uniaxially oriented film (polyester base material), and the weight of the solid content of the coating film with respect to the surface area of the uniaxially oriented film is 5.6 g / m ^2. As such, it was applied with a bar coater.

(Coating liquid for particle-containing layer)
A coating liquid for a particle-containing layer (coating liquid A) was prepared by mixing each of the components shown below. Filtration treatment of the prepared coating liquid A using a filter having a pore size of 6 μm (F20, manufactured by Mare Filter Systems Co., Ltd.) and membrane degassing (2x6 radial flow superphobic, manufactured by Polypore Co., Ltd.). Was applied to the surface of the uniaxially oriented film and dried in hot air at 100 ° C. to form an easy-to-slip coating layer.

A copolymer composed of an acrylic resin (methyl methacrylate, styrene, 2-ethoxyhexyl acrylate, 2-hydroxyethyl methacrylate and acrylic acid (containing in a mass ratio of 59: 8: 26: 5: 2)) is used as a solid content in 27. Water dispersion containing 5% by mass): 167 parts, nonionic surfactant ("Naroacty (registered trademark) CL95), manufactured by Sanyo Kasei Kogyo Co., Ltd., polyoxyalkylene alkyl ether, solid content 100% by mass): 0 .7 parts, anionic surfactant ("Lapisol (registered trademark) A-90", manufactured by Nichiyu Co., Ltd., 1% by mass water diluted solid content): 55.7 parts, wax ("Cerozol (registered trademark)) 524 ”, manufactured by Chukyo Oil & Fat Co., Ltd., ester wax dispersion, solid content 30% by mass): 7 parts, cross-linking agent (“Carbodilite (registered trademark) V-02-L2”, manufactured by Nisshinbo Chemical Co., Ltd., Carbodiimide compound, solid 10% by mass water diluted solution): 20.9 parts, non-aggregated particles ("Snowtex XL", average particle diameter 50 nm, colloidal silica, manufactured by Nissan Chemical Co., Ltd., 40% by mass aqueous dispersion with solid content): 2. 8 parts ・ Aggregated particles (“Aerodil OX50”, average secondary particle diameter 200 nm, aggregated silica, average primary particle size 40 nm, manufactured by Nippon Aerozil Co., Ltd., solid content 10% by mass aqueous dispersion): 2.95 parts ・ Water: 743 copies

<Transverse stretching process>
The film subjected to the longitudinal stretching step and the particle-containing layer forming step was stretched in the width direction using a tenter under the following conditions to prepare a biaxially oriented film.
(Transverse stretching conditions)
Preheating temperature: 100 ° C
Stretching temperature: 120 ° C
Stretching ratio: 4.3 times Stretching speed: 50% / sec

<Heat fixing process>
The biaxially oriented film subjected to the above-mentioned transverse stretching step was heated under the following conditions using a tenter to perform a heat fixing step of heat-fixing the film.
(Heat fixing conditions)
Heat fixation temperature T1: 227 ° C
Heat fixing time: 6 seconds

<Heat relaxation process>
Next, the heat-fixed film was heated under the following conditions to perform a heat relaxation step of relaxing the tension of the film. Further, in the heat relaxation step, the film width was reduced as compared with the end of the heat fixing step by narrowing the distance (tenter width) between the gripping members of the tenter that grips both ends of the film. The following heat relaxation rate ΔLr was obtained from the film width L2 at the end of the heat relaxation step with respect to the film width L1 at the start of the heat relaxation step by the formula Lr = (L1-L2) / L1 × 100.
(Heat relaxation conditions)
Heat relaxation temperature T2: 190 ° C
Heat relaxation rate Lr: 4%

<Cooling process and expansion process>
A cooling step of cooling the heat-relaxed film under the following conditions was performed. Further, in the cooling step, an expansion step was carried out in which the film width was expanded as compared with the time when the heat relaxation step was completed by widening the tenter width.
The cooling rate V below is the film surface temperature and the cooling unit 50 measured at the time of loading into the cooling unit 50, with the residence time from the time the film is carried into the cooling unit 50 of the stretching machine 100 to the time it is carried out as the cooling time ta. It was obtained by dividing the temperature difference ΔT (° C.) from the film surface temperature measured at the time of carrying out by the cooling time ta.
Further, the following expansion ratio ΔL was obtained from the film width L3 at the end of the cooling step with respect to the film width L2 of the polyester film at the start of the cooling step by the formula ΔL = (L3-L2) / L2 × 100.
(Cooling conditions)
Cooling speed V: 2500 ° C / min Cooling time ta: 3.1 seconds (expansion condition)
Expansion rate ΔL: 0.6%

<Rolling process>
With respect to the film cooled by the cooling step, the film was continuously cut along the transport direction at a position 20 cm from both ends in the width direction of the film using a trimming device, and both ends of the film were trimmed. Next, an extrusion process (knurling) was performed on a region from both ends of the film to 10 mm in the width direction, and then the film was wound up at a tension of 40 kg / m.
A biaxially oriented film was produced by the above method. The thickness of the obtained biaxially oriented film was 31 μm, the width was 1.5 m, and the winding length was 7000 m. The thickness of the particle-containing layer of the obtained biaxially oriented film was 40 nm. Further, as a result of measurement by the above method, it was confirmed that the particle-containing layer of the obtained biaxially oriented film contained particles having an average particle diameter of 50 nm and particles having an average particle diameter of 200 nm. ..

[Example 2]
A biaxially oriented film was produced according to the method described in Example 1 except that the coating liquid B having the same composition as the coating liquid A was used as the coating liquid for the particle-containing layer except that it did not contain non-aggregating particles. did.

[Examples 3 to 11]
The method according to Example 1 except that the heat fixing temperature T1 in the heat fixing step, the cooling rate V in the cooling step, and the expansion rate ΔL in the expansion step are controlled to be the values shown in Table 1 described later. A biaxially oriented film was prepared according to the above.

[Examples 12 to 17]
In Example 1, except that the particles shown in Table 1 were used as non-aggregated particles without containing agglomerated particles, and the thickness of the particle-containing layer was adjusted to the values shown in Table 1. A biaxially oriented film was prepared according to the method described.
Details of the particles listed in Table 1 are shown below.
450 nm non-aggregated particles: Snowtex MP-4540M, manufactured by Nissan Chemical Co., Ltd., average particle diameter 450 nm, colloidal silica 200 nm non-aggregated particles: Snowtex MP-2040, manufactured by Nissan Chemical Co., Ltd., average particle diameter 200 nm, colloidal silica 100 nm non-aggregated particles: Snowtex ZL, manufactured by Nissan Chemical Co., Ltd., average particle diameter 100 nm, colloidal silica 50 nm non-aggregated particles: Snowtex XL, manufactured by Nissan Chemical Co., Ltd., average particle diameter 50 nm, colloidal silica 300 nm non-aggregated particles Particles: Divinylbenzene / styrene copolymer crosslinked particles, average particle size 300 nm

[Example 18]
Instead of the extrusion molding step carried out in Example 1, the melt produced in the extrusion molding step of Example 1 and the melt of the following resin H are co-extruded into a cooling drum at 25 ° C. by co-extrusion molding. By doing so, a biaxially oriented film was produced according to the method described in Example 1, except that an unstretched film composed of polyethylene terephthalate and a particle-containing layer was produced.
Resin H pellets containing non-aggregated particles were produced according to the method for producing polyethylene terephthalate pellets in Example 1 except that divinylbenzene / styrene copolymer crosslinked particles having an average particle diameter of 300 nm were mixed. The obtained pellets are dried to a water content of 50 ppm or less, charged into a hopper of a uniaxial kneading extruder having a diameter of 30 mm, and then melted at 280 ° C. to produce a melt of resin H. did.
The thickness of the obtained biaxially oriented film was 31 μm, and the thickness of the particle-containing layer was 2 μm.

[Examples 19 to 21]
Described in Example 1 except that the thickness of the unstretched film made of polyethylene terephthalate was adjusted in the extrusion molding step so that the thickness of the produced biaxially oriented polyester film becomes the numerical value shown in Table 1. A biaxially oriented film was prepared according to the above method.
In Example 20, the coating liquid F was used as the coating liquid for the particle-containing layer.

[Example 22]
A biaxially oriented film was produced according to the method described in Example 1 except that the heat fixing temperature T1 was controlled to be the numerical value shown in Table 1 in the heat fixing step.

[Comparative Examples 1 to 5]
The heat fixing temperature T1 in the heat fixing step, the cooling rate V in the cooling step, and the expansion rate ΔL in the expansion step were controlled to be the values shown in Table 1 described later, and in Comparative Examples 1 to 4. A biaxially oriented film was produced according to the method described in Example 1 except that the coating liquid B was used as the coating liquid for the particle-containing layer.

[Measurement of physical properties]
The following physical properties were measured for each of the biaxially oriented films of Examples 1 to 25 and Comparative Examples 1 to 6. The measurement results are shown in Table 1.
Further, for each of the biaxially oriented films of Examples 2 to 25 and Comparative Examples 1 to 6, the thickness of the particle-containing layer and the average particle diameter of the particles contained in the particle-containing layer were measured according to the above-mentioned measuring method. The results of these measurements are also shown in Table 1.

<Density>
The density (g / cm ³ ) of the biaxially oriented film was measured using an electronic hydrometer (product name "SD-200L", manufactured by Alpha Mirage Co., Ltd.).

<Streak defect region (90 ° C, 120 ° C)>
The biaxially oriented film was heat-treated at 90 ° C. or 120 ° C. for 20 seconds while being conveyed at a transfer speed of 30 m / min and a tension of 100 N / m in the transfer direction using a heat transfer device. The heating temperature in the heat treatment refers to the surface temperature of the film. The heating time in the heat treatment was calculated from the time when the surface temperature of the film reached the target temperature (90 ° C. or 120 ° C.). The heat-treated biaxially oriented film was placed on a black flat plate, and then a fluorescent lamp installed on the ceiling of the room [Lupica Ace manufactured by Mitsubishi Electric Corporation (color temperature: 5000K, average color rendering index (Ra): 84). )] The biaxially oriented film was visually observed from an angle while changing the viewpoint so that the light was reflected. A region of 1 m × 1 m was visually observed, and a region where the reflected image of the fluorescent lamp was undulating on the surface of the biaxially oriented film was defined as a streak defect region. Next, the ratio (area ratio) of the total area of the observed streaky defect regions to the total area of the observation region of the biaxially oriented film was calculated by the method described above (see the item of "streaky defect region" above). ..

<Expansion rate (90 ° C, 120 ° C)>
The expansion coefficient of the biaxially oriented film in the width direction at 90 ° C. and 120 ° C. was determined by using a thermomechanical analyzer (TMA-60, manufactured by Shimadzu Corporation) as described above (see the item "Expansion rate" above). ).

<Maximum mountain height Rp>
For the maximum peak height Rp of the surface of the biaxially oriented film, the manufactured biaxially oriented film is cut out to prepare a test piece, and the surface of the obtained test piece is described above using the above-mentioned fine shape measuring device. The measurement was performed under the above conditions, and then particle analysis (multiple levels) was performed using the built-in analysis software.
To measure the maximum mountain height Rp, set the slice levels at equal intervals of 10 nm, measure the average diameter and density of each slice level 5 times while changing the measurement position, calculate the average value, and calculate the maximum. The measured value of the mountain height Rp was used. The test piece was fixed to the sample table so that the X direction of the visual field measurement was the width direction of the polyester film.

[evaluation]
The following evaluations were performed on each of the biaxially oriented films of Examples 1 to 22 and Comparative Examples 1 to 5. The evaluation results are shown in Table 1.

[Thickness unevenness]
While transporting the biaxially oriented film produced in each Example and Comparative Example, a coating liquid for a base layer composed of the following formulation A was applied to the surface of the biaxially oriented film using a slit-shaped nozzle, and then the temperature was 90 ° C. An underlayer was formed by drying the coating film under temperature conditions. Next, while transporting the biaxially oriented film on which the base layer is formed, a coating liquid for a black layer consisting of the following formulation B is applied onto the base layer, and then the coating film is dried under a temperature condition of 90 ° C. Formed a black layer. The transport speed of the biaxially oriented film when forming the base layer and the black layer was 70 m / min.
A biaxially oriented film provided with a base layer and a black layer was placed on a light table, and color unevenness of the black layer was visually observed at a position 1 m away from the biaxially oriented film.
A biaxially oriented film provided with the underlayer and the black layer was formed according to the above method except that the drying temperature conditions at the time of forming the underlayer and the formation of the black layer were both changed to 120 ° C., and visually observed. The observation was made at.
Based on the observation results of each biaxially oriented film produced with the drying temperature condition of the coating film set to 90 ° C. or 120 ° C., the thickness unevenness of the biaxially oriented film was evaluated according to the following criteria.

(Prescription A: Coating liquid for base layer)
-PVA205 (polyvinyl alcohol, manufactured by Kuraray Co., Ltd., saponification degree 88%, polymerization degree 550): 32.2 parts by mass-polyvinylpyrrolidone (manufactured by ISP Japan Co., Ltd., K-30): 14.9 parts-distilled water : 524 parts by mass, methanol: 429 parts by mass

(Prescription B: Coating liquid for black layer)
Resin-coated carbon black produced in accordance with paragraphs 0036 to 0042 of Japanese Patent No. 5320652: 13.1 parts by mass ・ Dispersant: Dispersant 1 according to paragraph [0103] of International Publication No. 2017/208849. 0.65 parts by mass ・ Polymer (benzyl methacrylate / methacrylic acid = 72/28 molar ratio random copolymer, weight average molecular weight 37,000): 672 parts by mass ・ Propropylene glycol monomethyl ether acetate: 79.53 Mass part

(Evaluation criteria)
A: No color unevenness of the black layer is confirmed in any of the drying temperature conditions of 90 ° C. and 120 ° C.
B: When the drying temperature condition was either 90 ° C. or 120 ° C., color unevenness of the black layer was slightly confirmed.
C: Color unevenness of the black layer was confirmed only when the drying temperature condition was 120 ° C.
D: Color unevenness of the black layer was clearly confirmed in both cases of the drying temperature condition of 90 ° C. and 120 ° C.

[Transfer failure]
Both ends were trimmed so that the width of the biaxially oriented film having the base layer and the black layer prepared in the evaluation of the thickness unevenness was 45 cm. Next, the trimmed biaxially oriented film was applied to an ABS (acrylonitrile-butadiene-styrene) resin winding core having a diameter of 3 inches (1 inch = 2.54 cm) while pressing a contact roller with a tension of 11.5 kg / m. Wrapped around. The length of the wound biaxially oriented film in the longitudinal direction was 100 m.
The obtained test piece was allowed to stand for 30 days under the conditions of 25 ° C. and 50% RH. After 30 days, the surface of the black layer in the biaxially oriented film wound around the winding core was exposed to a fluorescent lamp [Lupica Ace manufactured by Mitsubishi Electric Corporation (color temperature: 5000K, average color rendering index (Ra): 84)]. Observed under. The unevenness of the film surface was visually observed by the reflected light of the fluorescent lamp, and the transfer failure was evaluated according to the following criteria.

(Evaluation criteria)
A: No surface irregularities are seen, and the condition is extremely good.
B: Some surface irregularities are visible, but they are very slight irregularities.
C: Minor surface irregularities can be visually recognized.

Table 1 shows the evaluation results of each Example and Comparative Example.
In Table 1, the "forming method" column of the "particle-containing layer" means that the particle-containing layer was formed by the following method as the particle-containing layer forming step in each Example and Comparative Example.
A: Formed by applying a coating liquid on a uniaxially oriented film after the longitudinal stretching step and before the transverse stretching step (in-line coating method).
B: Formed at the same time as the unstretched film by coextrusion molding.

From Table 1, Examples 1 to 22 in which the cooling rate V of the polyester film in the cooling step is in the range of 2200 to 3500 ° C./min and satisfy the above condition 1 are compared with Comparative Examples 1 to 5. It was confirmed that uneven thickness of the functional layers to be laminated can be suppressed.
Further, from Table 1, Examples 1 to 22 in which the area of the streak defect region observed on the polyester film is 40% or less of the total area of the observation region after the specific heat treatment is performed are Comparative Examples. It was confirmed that the thickness unevenness of the functional layers to be laminated can be suppressed as compared with 1 to 5.

Above all, from the comparison of Examples 1 to 5 and 9 to 11, the absolute value of the value C, which is the product of A calculated by the formula (1) and B calculated by the formula (2), is 0.1. When it is ~ 0.7, it is confirmed that the thickness unevenness of the laminated functional layers can be further suppressed, and when the above value C is 0.1 to 0.5, the thickness unevenness of the laminated functional layers is further suppressed. It was confirmed that it could be suppressed.

Further, from the comparison of Examples 1 and 6 to 8, when the cooling rate V in the cooling step is 2200 to 3000 ° C., the thickness unevenness of the functional layers to be laminated can be further suppressed, and it is 2300 to 2600 ° C./min. In this case, it was confirmed that the thickness unevenness of the functional layers to be laminated can be further suppressed.

Further, from the comparison of Examples 1 and 12 to 17, it was confirmed that the transfer failure can be further suppressed when the maximum mountain height Rp of the surface of the particle-containing layer is 0.2 μm or less.
Further, by comparison between Examples 12 and 18, it was confirmed that when the particles contained in the particle-containing layer are resin particles, transfer failure can be further suppressed.
Further, from the comparison of Examples 1 and 12 to 17, it was confirmed that the transfer failure can be further suppressed when the particles have an average particle diameter of 0.4 μm or less.

[Example 23]
Using the biaxially oriented film prepared in Example 1 as a support, a transfer film for decoration was prepared by the following procedure.
The thermoplastic (non-photosensitive) resin layer coating liquid described in [0106] of International Publication No. 2017/208849 is applied to the surface of the biaxially oriented film produced in Example 1 on the side opposite to the particle-containing layer. Then, it was dried at 80 ° C. to form a thermoplastic (non-photosensitive) resin layer. Subsequently, a coating liquid for a base layer made of the above-mentioned formulation A was applied and dried at 120 ° C. to form a base layer. A composition for forming a photosensitive resin layer comprising the following formulation C was applied thereto and dried at 90 ° C. to form a photosensitive resin layer. The thickness of the base layer was 1.6 μm, and the thickness of the photosensitive resin layer was 2.0 μm. Finally, a polypropylene film having a thickness of 12 μm was pressure-bonded to the surface of the photosensitive resin layer as a protective film to prepare a transfer film for decoration.
The obtained decorative transfer film had good characteristics without color unevenness and transfer failure. Further, when the decorative transfer film was used to form a decorative pattern with reference to the description in [0109] of International Publication No. 2017/208849, a good pattern could be formed.

<Prescription C: Composition for forming a photosensitive resin layer>
・ 180.9 parts of the above-mentioned black pigment dispersion ・ A-NOD-N (Shin Nakamura Chemical Industry Co., Ltd., bifunctional, molecular weight 226) 3.29 parts ・ A-DCP (Shin Nakamura Chemical Industry Co., Ltd., Bifunctional, molecular weight 304) 9.9 parts, 8UX-015A (Taisei Fine Chemical Co., Ltd., 15 functionals) 6.59 parts, A-DPH (Shin Nakamura Chemical Industry Co., Ltd., 6 functionals, molecular weight 578) 2.20 Department
・ Binder (polymer of benzyl methacrylate / methacrylic acid, 70/30% by mass, weight average molecular weight (Mw) = 5000, solid content = 40.5% by mass) 141.2 parts ・ Polymerization initiator OXE-02 (BASF) IRGACURE OXE 02, Etanone, 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazole-3-yl]-, 1- (0-acetyloxime)) 6.75 parts, propylene glycol 250 parts of monomethyl ether acetate, 404.2 parts of methyl ethyl ketone

[Example 24]
Using the biaxially oriented film prepared in Example 21 as a support, a dry film for forming a touch panel protective film was prepared by the following procedure.
A coating liquid for forming a second transparent transfer layer having the following formulation D was applied to the surface of the biaxially oriented film produced in Example 21 on the opposite side of the particle-containing layer, dried at 90 ° C., and the second transparent transfer was performed. Formed a layer. Next, a coating liquid for forming a first transparent transfer layer consisting of the following formulation E was applied onto the second transparent transfer layer and then dried at 70 ° C. to form the first transparent transfer layer. The thickness of the second transparent transfer layer was 5.0 μm, and the thickness of the first transparent transfer layer was about 80 nm. Finally, a polyethylene terephthalate film having a thickness of 16 μm was pressure-bonded to the surface of the first transparent transfer layer as a protective film to prepare a transfer film for forming a touch panel protective film.
The obtained transfer film had no change in the refractive index due to uneven thickness, no transfer failure, and had good characteristics. When contact holes were formed in the obtained transfer film with reference to [0122] to [0128] of International Publication No. 2018/186428, a good pattern could be formed.

<Prescription D: Coating liquid for forming the second transparent transfer layer>
・ Aronix TO-2349 (Toa Synthetic Co., Ltd., carboxylic acid-containing monomer) 0.93 parts ・ A-DCP (Shin-Nakamura Chemical Industry Co., Ltd., bifunctional, molecular weight 304) 5.6 parts ・ 8UX-015A (Taisei) Fine Chemical Co., Ltd., Urethane acrylate) 2.80 parts, binder (polymer of cyclohexylmethacrylate / methyl methacrylate / methacrylate / glycidyl methacrylate adduct of methacrylic acid, 51.5 / 2 / 26.5 / 20%, Weight average molecular weight (Mw) = 29000, acid value = 95 mgKOH) 15.59 parts-Polymer initiator IRGACURE OXE-02 (BASF) 0.11 parts-Polymer initiator IRGACURE 907 (BASF, 2-methyl-1- (4-Methylthiophenyl) -2-morpholinopropane-1-one) 0.21 part ・ N-phenylglycine 0.03 part ・ Blocked isocyanate (Asahi Kasei Chemicals Co., Ltd., Duranate WT32-B75P) 3.63 parts ・Benzoimidazole 0.09 part ・ Initiator (DIC Co., Ltd., Megafuck F-551) 0.02 part ・ 1-methoxy-2-propyl acetate 31.08 part ・ Methyl ethyl ketone 40.0 part

<Prescription E: Coating liquid for forming the first transparent transfer layer>
・ Nanouse OZ-S30M (ZrO ₂ particle methanol dispersion, Nissan Chemical Industry Co., Ltd., non-volatile content 30.5%) 4.34 parts ・ Ammonia water (25%) 7.82 parts ・ Monoisopropanolamine 0.02 parts・ Binder (allyl methacrylate / methacrylic acid copolymer, 40/60 mol%, weight average molecular weight (Mw) = 38000) 0.24 part ・ Aronix TO-2349 (Toa Synthetic Co., Ltd.) 0.03 part ・ Bentotriazole 0 .03 parts ・ Surfactant (DIC Co., Ltd., Megafuck F-444) 0.01 parts ・ Ion exchanged water 21.5 parts ・ Methanol 66.0 parts

[Example 25]
Using the biaxially oriented film prepared in Example 21 as a support, a dry film for forming an etching resist was prepared by the following procedure.
A coating liquid for forming a thermoplastic resin layer consisting of the following formulation F was applied to the surface of the biaxially oriented film produced in Example 21 on the opposite side of the particle-containing layer, and dried at 80 ° C. to form a thermoplastic resin layer. Formed. Next, a coating liquid for forming a water-soluble resin layer consisting of the following formulation G was applied onto the thermoplastic resin layer and then dried at 80 ° C. to form a water-soluble resin layer. Further, a coating liquid for forming a photosensitive resin layer consisting of the following formulation H was applied onto the water-soluble resin layer and then dried at 80 ° C. to form a photosensitive resin layer. The thickness of the thermoplastic resin layer was 2 μm, the thickness of the water-soluble resin layer was 1 μm, and the thickness of the photosensitive resin layer was 2 μm. Finally, a polyethylene terephthalate film having a thickness of 16 μm was pressure-bonded to the surface of the photosensitive resin layer as a protective film to prepare a transfer film for forming an etching resist.
When the obtained transfer film was exposed with reference to [0429] to [0430] of International Publication No. 2019/151534 and the visibility was confirmed, the line and space pattern was clearly visible.

<Prescription F: Coating liquid for forming a thermoplastic resin layer>
・ Polymer of benzyl methacrylate / methacrylic acid / acrylic acid (75/10/15 mass%, molecular weight 30,000, solid content concentration 30%) 22.7 parts ・ 3,6-bis (diphenylamino) fluorane 0.12 parts A-1, oxime sulfonate type photoacid generator 0.2 part, tricyclodecanedimethanol diacrylate 3.32 part, 8UX-015A (Taisei Fine Chemical Co., Ltd.) described in paragraph 0227 of JP2013-047765A. ), 15 functional parts) 1.66 parts ・ Aronix TO-2349 (Toa Synthetic Co., Ltd.) 0.55 parts ・ Surfactant (DIC Corporation, Megafuck F-552) 0.02 parts

<Prescription G: Coating liquid for forming a water-soluble resin layer>

-Polyvinyl alcohol (Kuraray Poval 4-88LA, manufactured by Kuraray Co., Ltd.) 3.22 parts-Polyvinylpyrrolidone (manufactured by Nippon Catalyst Co., Ltd., K-30) 1.49 parts-Surfactant (Megafuck F-444, DIC Co., Ltd.) 0.0035 parts, methanol (Mitsubishi Gas Chemical Co., Ltd.) 57.1 parts, ion-exchanged water 38.12 parts

<Prescription H: Coating liquid for forming a photosensitive resin layer>
・ Polymer of styrene / methacrylic acid / methyl methacrylate (52/29/19 mass%, molecular weight 60,000, solid content concentration 30%) 25.2 parts ・ Leuco crystal violet 0.06 parts ・ Photopolymerization initiator (2) -(2-Chlorophenyl) -4,5-diphenylimidazole dimer) 1.03 parts · 4,4'-bis (diethylamino) benzophenone 0.04 parts · (N-phenylcarbamoylmethyl-N-carboxymethylaniline 0) .02 parts ・ ethoxylated bisphenol A dimethacrylate NK ester BPE-500 (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.) 5.61 parts ・ Aronix M-270 (manufactured by Toa Synthetic Co., Ltd.) 0.58 parts ・ Phenothiazine 0. 04 parts ・ 4-Hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidone 0.002 parts ・ Initiator (DIC Co., Ltd., Megafuck F-552) 0.048 parts ・ Propropylene glycol monomethyl ether acetate 19 .7 parts ・ Methyl ethyl ketone 43.8 parts

[Example 26]
Using the biaxially oriented film produced in Example 1 as a support, a release film for producing a ceramic green sheet was produced by the following procedure.
A coating liquid for forming a release layer consisting of the following formulation J was applied to the surface of the biaxially oriented film produced in Example 1 on the opposite side of the particle-containing layer, and dried at 120 ° C. to form a release layer. The thickness of the release layer was 0.1 μm. Next, a ceramic slurry consisting of the following formulation K was applied onto the release layer so that the thickness after drying was 0.5 μm, and then dried at 90 ° C. The slurry surface and the particle-containing layer surface were overlapped with each other, and ^{a load of 1 kg / cm 2} was applied for 10 minutes, and then the release film was peeled off to obtain a ceramic green sheet.
The obtained ceramic green sheet had good characteristics without uneven thickness or transfer failure.

<Prescription J: Coating liquid for forming a release layer>
・ Silicone resin (manufactured by Tohredo Dow Corning Co., Ltd., SRX-345, addition reaction type silicone) 10 parts ・ Platinum catalyst (manufactured by Tohredo Dow Corning Co., Ltd., SRX-212) 0.1 parts ・ Toluene / methyl ethyl ketone mixed solvent 490 copies

<Prescription K: Ceramic Rally>
・ Polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd., Eslek BH-3) 5 parts ・ Barium titanate (manufactured by Fuji Titanium Industry Co., Ltd., HPBT) 50 parts ・ Toluene / ethanol mixed solvent 45 parts

2a-2l: Grip member 10: Preheating part 20: Stretching part 30: Heat fixing part 40: Heat relaxation part 50: Cooling

part

60a, 60b: Circular rail 100: Stretching machine 200: Film P, Q: Gripping release point MD: Transport direction (longitudinal direction)
TD: Width direction L0, L1, L2, L3: Film width

Claims

An extrusion molding step of extruding a molten resin containing polyester into a film to form an unstretched polyester film containing at least a polyester base material.
A longitudinal stretching step of stretching the unstretched polyester film in the transport direction to form a uniaxially oriented polyester film.
A transverse stretching step of stretching the uniaxially oriented polyester film in the width direction to form a biaxially oriented polyester film.
The heat fixing step of heating and heat-fixing the biaxially oriented polyester film,
A heat relaxation step of heating the polyester film heat-fixed by the heat fixing step at a temperature lower than that of the heat fixing step to relieve heat.
A cooling step of cooling the polyester film heat-relaxed by the heat-relaxation step, and a cooling step of cooling the polyester film.
The cooling step comprises an expansion step of expanding the heat-relaxed polyester film in the width direction.
A method for producing a polyester film comprising a polyester base material and a particle-containing layer containing particles on at least one surface of the polyester base material.
The cooling rate V of the polyester film in the cooling step is 2200 to 3500 ° C./min, and
A method for producing a polyester film that satisfies the following condition 1.
Condition 1: The melting point of the polyester is Tm (° C.), the heat fixing temperature in the heat fixing step is T1 (° C.), the draw ratio of the uniaxially oriented polyester film in the transverse stretching step is a, and the heat in the expansion step. When the percentage of the expansion rate in the width direction of the relaxed polyester film is b (%), the value C which is the product of A calculated by the following formula (1) and B calculated by the following formula (2). However, it is -4.0 to 4.0. However, this excludes cases where only one of A and B is 0.
A = Tm-T1-30 (1)
B = a / 5-b (2)
The manufacturing method according to claim 1, wherein the value D calculated from the A, the B, and the cooling rate V by the following formula (3) is 1 to 10000.
D = (A x B) 2 x V (3)
The manufacturing method according to claim 1 or 2, wherein the thickness of the polyester film is less than 50 μm.
Between the longitudinal stretching step and the transverse stretching step, there is further a step of forming the particle-containing layer using a coating liquid containing the particles, or
One of claims 1 to 3, further comprising a step of forming the particle-containing layer by extruding a second melt containing the particles and a binder at the same time as the molten resin in the extrusion molding step. The manufacturing method described in.
The production method according to any one of claims 1 to 4, wherein the surface temperature T2 of the polyester film in the heat relaxation step is 210 ° C. or lower.
The production method according to any one of claims 1 to 5, wherein the cooling rate V of the polyester film in the cooling step is 2200 to 3000 ° C./min.
The manufacturing method according to any one of claims 1 to 6, wherein b is more than 0% and 1.2% or less.
With polyester base material,
A particle-containing layer containing particles on at least one surface of the polyester substrate.
Is a polyester film with
The thickness of the polyester film is less than 50 μm, and the thickness is less than 50 μm.
The polyester film was heat-treated for 20 seconds under the condition that the temperature of the film surface was 90 ° C. while transporting the polyester film under the conditions of a transport speed of 30 m / min and a tension of 100 N / m in the transport direction. A polyester film in which the total area of streaky defect regions observed in the polyester film is 40% or less of the total area of the observation region.
The polyester film according to claim 8, wherein the expansion rate in the width direction of the polyester film at 90 ° C. is −0.15 to 0.15% with respect to the dimension in the width direction of the polyester film at 30 ° C.
The polyester film according to claim 8 or 9, wherein the polyester film has a density of 1.39 to 1.41 g / cm 3.
The thickness of the polyester base material is 3 to 40 μm, and the thickness is 3 to 40 μm.
The polyester film according to any one of claims 8 to 10, wherein the particle-containing layer has a thickness of 0.001 to 2.5 μm.
The polyester film according to any one of claims 8 to 11, wherein the particle-containing layer contains particles P having an average particle diameter of 10 nm or more and less than 1 μm.
The polyester film according to claim 12, wherein the average particle diameter of the particles P is larger than the thickness of the particle-containing layer.
The polyester film according to any one of claims 8 to 13, wherein the particle-containing layer contains particles P1 having an average particle diameter of 10 to 100 nm.
The polyester film according to any one of claims 8 to 14, wherein the particle-containing layer contains particles P2 having an average particle diameter of more than 100 nm and 400 nm or less.
The particles contained in the particle-containing layer are resin particles or
The particles contained in the particle-containing layer are inorganic particles, and the maximum mountain height Rp of at least one surface of the polyester film is 5 to 200 nm.
The polyester film according to any one of claims 8 to 15.
The polyester film according to any one of claims 8 to 16, wherein the polyester base material does not substantially contain particles.
The polyester film produced by the production method according to any one of claims 1 to 7, or the polyester film according to any one of claims 8 to 17, wherein one surface of the polyester base material is used. A polyester film having a particle-containing layer only on the top,
A functional layer selected from the group consisting of a decorative layer, a photosensitive resin layer, and a peeling layer, which is on the surface of the polyester substrate opposite to the particle-containing layer.
Has a laminated film.
The laminated film according to claim 18, wherein the functional layer is a decorative layer and the laminated film is a decorative film.
The laminated film according to claim 18, wherein the functional layer is a photosensitive resin layer and the laminated film is a photosensitive transfer film.
The laminated film according to claim 18, wherein the functional layer is a release layer, and the laminated film is a release film for manufacturing a ceramic green sheet.